So, I'm posting this in the hopes that someone with more experience in 3D art can give me some insights. As you might guess from my avatar, I have some very basic grasps of how to mess around with layers and whatnot...

The default skill icons I use as a guide are under Textures\menus\Class\Attributes\ in the textures.bsa file

I'm trying to create new icons for the game's skills, and I seem to have the preliminary hang of it with GIMP: using a base image, first I resize it to 241x348 pixels and 72x72 ppi resolution, save it, then I resize the canvas so that it ends at 512x512 pixels, and export it as a DDS with BC2\DXT3 compression. I have no good method to create the small version, other than manually selecting a square more or less suitable from the previously saved image, resizing it to 64x64 pixels and exporting it the same way.
I'm not sure if that is the same compression that the vanilla icons use, or if I should generate mipmaps for them, but so far they do work correctly in game.

The thing is, ideally I'd like the icons I make to have similar artstyle to http://elderscrolls.wikia.com/wiki/Category:Oblivion_Icons, and while the foreground picture for the icon itself might be not too hard to find/create, I don't know how to create image backgrounds similar to the ones there. Even a way to somehow isolate the background designs from the vanilla skill icons to apply them to my own would suffice me.

If you can suggest any method to achieve such a thing, either with GIMP or Photoshop or whatever image editing software you use (I'm confident they can be replicated in GIMP) I'd be grateful.