How to get access to previous version's textures?

I'm trying to make a resource pack using 12w34a leather armor. I already have the model texture, the actual armor texture, but I'm now looking for the item texture. What I mean for the item texture is the actual item itself, like if you were creating a leather helmet.

EDIT: To put more clarity of my request, I'm looking for 12w34a Item texture NOT model textures.

1. Start the Minecraft version you want the textures of.
2. Exit the game. (optional)
3. Go to %appdata%\.minecraft\versions. (paste it into the path bar of Windows explorer like this)
4. Open the folder with the version name you want.
5. Open or unpack the .jar file with 7zip (archive) or another archiving program.
6. There the textures are, but in a different structure in different versions. In 1.3.2 for example the texture you want is gui/items.png in the top left.

For downloading old snapshots, you can look in the wiki, for example the 12w34a wiki page (archive) links to a download of the snapshot (archive).
For installation of old snapshots, read this tutorial (archive).