I have found that going back into traditional art, even art that I never found myself relating to in the past, has been very helpful to my inspiration. Go to an art museum gift shop and spend an hour or two going through art books. Or like Eraserhead said, try something like photography or attending drawing labs.
I know that sometimes when I use to draw a lot, that I'd start to notice that I seemed to be decreasing in skill. What I would then do is not draw for a while (talking like weeks or even a month or two) and then hop back on the doodle train and I'd have tons of ideas. 3D for me is a little different, it's harder for me to…