Images that are in App_Data folder not shown in browser

The App_Data folder is a special folder reserved for data such as database files and so on, and will NOT render out any contents on the web. This is by design, and intentional and cannot be changed (as far as I know).

Your images do definitely not belong into the App_Data subfolder - put them into a /images folder or something more appropriate.

Images should never be stored in the App_Data Folder. This is reserved for files that should never be served to the user directly, such as .mdb database files, etc.

I would create a /Resources or /Resources/Images folder off the root of the site.

I disagree. When hiding images in the App_Data folder and creating your own http-handler you secure your images and can add copyright-text etc. on the images before you show them.

I do this when I have highres pictures i don't wan't everybody to get, and having the http-handler downscale the image and put on some copyrighttext. Great!