I have used photo-backgrounds in some of my artwork here on NG. (Can you guess which ones? probably...) I think what makes it acceptable or not is how much the photo adds to the image. If the photo is holding up the artwork like a crutch, then it is not acceptable. If the artwork could work without the photo or if the photo is blended seemlessly, it's acceptable. As for Karsys, the image Lonely Town is interesting because there is an amusing juxtaposition going on. For a lot of the other artwork there, the photos seem to be thrown around randomly, not necessarily bailing out the work, but they're not used very skillfully either.
As for artists bashing photographic reference, I think that's something different. Art is at its core a form a narrative, a way to convey information to someone else. If I draw a pretty girl, the artwork stands in for a lengthy description of a pretty girl. But sometimes, the narrative of art is not about the subject of the artwork but about art itself. For example, Picasso's Demoiselles d'Avignon is a painting of naked women, but the narrative is about perspective and anatomy and artistic convention, which makes it interesting to art scholars, but the average eye doesn't really get it. When you're drawing something from photographic reference, the narrative isn't about the thing you're drawing, the narrative is about your skill at capturing photorealism, you're just showing off, and the gut reaction from cartoonists is "fuck you, I don't need to capture realism to be a good artist" or at least "you're missing the point".
Anyways, Karsys, in examining your own art, think about what is your narrative. In Dino in the Desert, are you trying to give people a narrative about extinct animals and arid climates, or is this a drawing about the way things are drawn? If it's supposed to funny (which seems to be your way) ask, could it be funnier? should it be funnier? Do other people share this sense of humor? Does the artwork offer anything to people who don't find it funny?