I agree- I'm not a great fan of program specific catagories. I often make my images in layers(duh).  The BG from Vue often, a few poser items, Some PS clouds and post work. There is a big problem with useing the mixed medium catagory beyond the number of views. It's the one catagory that is rejected by staff for things like AOM, AOY ect..............
Personally, I'd perfer catagories like the book catagories. Fiction, Fantasy, Sci-fi, Biography, science   ect ect.........