Custom map item/entity in Bedrock edition?

I'm wondering if it's possible to make a custom map item/entity like either of the default maps provided with Minecraft.

I can't find anything in the vanilla resource pack sample, nor on the web, and as such I presume the answer is it's not possible.

How can I create a custom map item/entity?

NOTE: The very detailed answer by @Jithin, is amazing, but not what I'm looking for. I'm looking to create an entirely new item in a custom resource pack, that functions like a map. For example, something like:

...
"minecraft:client_entity": {
    "description": {
        "identifier": "tacosontitan:custom_map",
        "materials": { "default": "map" },
        "textures": { "default": "textures/items/custom_map" },
        ...

Look at the following tool:

Before you get started, you’ll need to have a few things ready:

An Internet connection. Since this is a browser-based tool, you’ll need to be able to get online so you can use the website. An image you want to bring in as a picture. You’ll also want to know the dimensions of the image, and for best results make sure those dimensions are easily divisible into clean integers (1, 2, 3, 4…). More on this in step 1. The total number of Maps that already exist in your world. You can find this by opening your world’s folder on your computer or server, then going into the data sub-folder, and looking at the number of maps shown there. (Here’s how to find that folder)

This world has 166 maps, including map_0.dat

A location in your world that no one will EVER travel to. Using a world border, you can make sure that you pick a coordinate that is outside of the boundary. More on this later. Once you have all of those things together, you can follow the steps below. On first glance it might look like a long process, but we’re just being detailed here to prevent any confusion. Once you understand the steps, you’ll be able to add more maps in the future really fast.

Step 1. Prepare Your Image If you want to have a great looking picture in your builds, you’re going to need to set up your image file properly first. You don’t want to place your picture down in the world only to find that it’s stretched, squashed, or cropped in some weird way.

We’re going to use an image that we’ve already set up and placed in the world as an example here. This Villagered poster will do quite nicely.

Also a shameless plug for a new 1.14 server coming soon.

Now, this image is already set at the correct dimensions. We know that we have a wall with a 3×4 area where we want the image to go, so we made sure that the image’s dimensions are at the same 3×4 ratio. Specifically, this image is 1,728 pixels (18 inches) wide by 2,304 pixels (24 inches) tall.

If you want to fill a 5×5 wall with one massive picture, you can follow the same logic. Get the image on your computer and using a tool like GIMP or Photoshop you can edit it to have the same 5×5 ratio. Something like 2,000 pixels by 2,000 pixels might be good, or even larger at 3,000 pixels by 3,000 pixels. Both of those will fit the same shape and dimensions.

Step 2. Prepare Your Wall You may have already done this before you even started Step 1, but here’s a quick reminder: You’re going to need a wall with item frames.

Since our image is 3×4, We made a solid wall with 3 item frames going across, and 4 item frames going down. We also put glowstone behind the four corners, though you may want to put glowstone (or any light-emitting block) behind all of the item frames depending on the size of your picture. Without proper lighting, your final picture will look a bit pixellated due to the lighting differences from one block to another, so you might as well get that set up now.

Here’s what your wall should look like. Notice the glowstone, too!

Step 3. Prepare Your MC Map Tool Settings Now that your image and wall are both prepped, there’s one last step before you can upload your image using the MC Map Item Tool. Head to the Settings page on that website to make any adjustments to fit your needs, but most importantly you’ll want to adjust the X center and Z center values.

You can copy these settings exactly as they are for this tutorial.

For our purposes, we have a world border set up in the world that has a radius of 20,000 blocks, so setting the X center and Z center to 999,999 blocks away from spawn will perfectly prevent anyone from venturing into that area and messing up the pictures. Set those fields to whatever number you’d like, and then click “Save settings” before moving on to Step 4.

Step 4. Upload Your Image Alright, your image is edited, the item frames are in place, and your tool settings are saved. It’s time to start creating these map files.

Start by heading back to the tool’s home page and click the button to upload your image.

Step 5. Adjust The Size Next you’ll see a page which has two dropdown boxes at the top, along with an example of your image and the settings you saved at the bottom. You’ll notice that your image probably looks squashed or stretched right now. That’s OK! This is just to show you that you uploaded the correct image.

At this point we need to change the two dropdown boxes to match the size area you set up in Step 2. Since our image is 3×4, we selected “3” for the Horizontal setting and “4” for the Vertical setting, like the image below. Once you’ve selected the right options, click the “Select number” button.

Step 6. Review Your Map Parts The next page you’ll see doesn’t have any settings you need to change, but it does give you one last chance to look over your image and each individual map part before the files are rendered. This is your chance to see if the image will be skewed or squashed, if any of it looks strange after the colors are converted, or if a part of the image is missing. If so, you may need to go back to Step 1 and re-adjust your image to fit better.

If everything looks good, though, click the “Adjust colors” button to continue.

Step 7. Create The Maps In Game Here’s where things might get a little tricky.

We know that the image’s size is 3×4. Well, that means we’re going to have 12 maps total that will be rendered using the MC Map Item Tool.

We need to create those 12 maps in the game before doing anything else.

If you’re in creative mode, this is as simple as grabbing an empty map from the creative inventory and right-clicking it 12 times to create 12 different filled maps with unique IDs. If you’re in Survival mode, you’ll need to craft the 12 empty maps and then right-click on all 12 of those to make them filled maps. It doesn’t matter what your filled maps look like. They can all be of the exact same area in your world. But you need to make them first before we can go further with the tool.

Once you’ve created your 12 maps (or however many you need), save your world or server and exit out of the world. Don’t go back in until we get through the next few steps.

Step 8. Tell The Tool How Many Maps You Have Remember that total number of maps you found at the beginning of this process? Now’s the time when we’re going to use that number.

Go back to your web browser where you left off after Step 6, and you’ll see a question waiting for you to answer, “How many maps does your world already have?”. This field is where you put in that number we got at the beginning. For us, since we saw map_165.dat in our /world/data/ folder, we know that there are 166 maps already created in that world. So, we type in “166”.

If your world is brand new and has had no maps created yet, just set it to “0”. Once you’ve typed in the correct number, click the “Create file” button.

NOTE: If you type in the wrong number here, your picture will not show up in the game and you may even lose previously generated maps. Be careful to type the correct number.

Step 9. Download And Extract The Map Files Finally. We’ve made it to the last step where we need the web browser. At this point the tool will give you a link to download a zip folder of your map files. Click on that to save the file to your computer, and then use a zip extracting tool (most computers have one built in by right-clicking the downloaded file, but you can also try 7zip) to extract all of the map files from that zip.

What you’ll end up with is a folder showing all of the newly generated map files, 12 in total if that’s the size of the picture you selected earlier, all numbered based on the total number of maps in your world set in Step 8. Here you can see I have maps number 166 through 177 all ready to go.

Step 10. Move The New Maps To Your World’s /data/ Folder If you go over to your /worldname/data/ folder (here’s how to find that folder), you should see those same maps in there. These are the maps you created in Step 7, and do not match the maps you just downloaded using the tool.

Now all you have to do is copy the new maps you downloaded over to this /worldname/data folder and overwrite the existing files there.

Step 11. Place The Maps In Game That’s it! You’ve now got your maps ready to be loaded in the game and placed on the wall. Log back into your world and you’ll see the maps that were in your inventory all look drastically different than before.

Simply place those maps in the item frames that you set up in Step 2, and your new picture will look beautiful on the wall.

Enjoy Your New Pictures Want to add more custom pictures to your Minecraft world, or even give them out as rewards to players on your server? Just follow those steps for each new map picture you want to create, and you’ll have something in your world that is entirely unique to you.

One last note: Keep in mind that item frames and maps are entities and can therefore cause FPS lag if you have too many of them in a small area. Try not to make massive banners or your game could lag and even crash. Be especially mindful of this if you’re adding these on a multiplayer server.

Source: https://snapshotmc.com/2019/05/01/use-this-tool-to-create-custom-map-and-banner-art-in-minecraft-fast/.