I realize this question doesn't just involve the creation kit and actually probably involves the kit very little. I've searched online and I can't seem to find a hi-resolution tutorial. I've seen a few videos involving gimp but I would say just about all of them involve re-texturing a piece of armor etc. and they don't show how to do 2k, 4k textures- typically it's just a solid color.

Sorry for such a rookie question.

Are you thinking you can upscale existing textures?

It's real hard to take low res and go hi res, as there is no extra information to use, you have interpolate or extrapolate the missing data. This thread describes how one person did it, but the process seems to take as much time as reskinning it would. Going from Hi-Res to low is much easier.

http://forums.newdoom.com/showthread.php?t=34576

Here is how to Reskin for more detail, which does not always mean more resolution

http://www.webdesign.org/photoshop/textures-patterns/page-1.html