Ah maybe it needs an Alpha channel but that might not be right as jpegs don't have them. Bmp's do as does some png's maybe turn off the alpha in the surface's so I-ray won't look for one. I still might be wrong!! i just remember seeing something like this years ago fracking fog textures did something like this to me and it was the alpha at fault. regular windows paint can see and save alphas i would not think a background or dome would need a alpha...Glass etc effects do some times