UVs don't need to change, they're relative only to the texture.
That is to say, when the UVs are
0 0
0 0.5
0.5 0.5
0.5 0
That is:
So you match that order with the order of the four positions of the quad to map the image onto the face. UV coords can be copied over easily.
I dunno how the normals need to be changed on angled faces to make them light properly though, I think when you have them all facing directly out from the face it gets that weird flat lighting.