I believe that the photographers at the DMV are specially trained to take bad photos, I've never seen one where the person's picture didn't resemble a mug shot or sometimes, as with my mom, a corpse in the morgue. I know they're in a hurry but just a little care on their part is all that's needed.
I don't think they are trained at all. If they are, they are trained for something, but not photography (probably arts).
My actual licence pic is pretty good, but I once went to school in the US and got one of the mugshot-types. On both my drivers license and ID card you could see the top of the blue screen and part of the wall behind it.