That's why I love being part of a Daily Sketch community. With daily prompts I always have an idea on what to paint, and If i'm not feeling it I can do a quick rough sketch and that's still ok.
Is that on Snapzu? I created /t/artrequest in the spirit of that idea, so maybe you'd like to check it out?
I'll take a look, at the moment I was still using reddit's r/sketchdaily.