Well, I picked an image at random and applied on Hyrule Castle's background to test if replacing the background with a 4X image was possible. It seems that it can be replaced without any noticeable problems (I have no idea if these enhancements "eats" your video cards, working fine here).
It would be nice to find/make a decent replacement background as close as the original as possible. I post the original one if for some reason someone can improve it or find a decent replacement.
Anyways, I'll continue with the regular textures for now
EDIT: I figured that the background is missing the top and bottom textures. I'll upload the correct dumps later :huh: