I'm just curious, but are there any mods that use new graphics (sprites or backgrounds) for map levels?
Sorry I missed this originally ... If mods includes the Co8 modpack itself, then yes - many many maps are custom maps. The graphics used are from the vanilla game, reorganized creatively to make new environments. Then there a great many in KotB that were built from the ground up. I believe that there are a few new sprites, but they are existing ones with new meshes added and that sort of thing. See the Models and Animations forum for more info.