Oh, yeah, I forgot to mention I'm using NURBs, so I can't apply a material to only some faces (or at least I don't know how to do that if it is possible). I think the closest thing I could do is cut the surface in two and then apply white only to the inside and picture to the outside, but I would rather stay with one single surface (and also with NURBs).

Is there anyway to fix that problem with a single NURB surface?

Thanks.