Do you have problems with textures on large surfaces? I find in Blitz the moment a texture, whether on quad or skydome or whatever, is stretched to maybe 75%+ of the screen area, there's a terrible performance hit. The idea of a full-screen background, either as a copied image or textured quad, just hasn't been practical. For my current project's UI I've sliced the full-screen interface into several sections. My next project is space-bound and a full-screen nebula backdrop would be nice, but performance wise I don't think it's viable.