Well, a work in progress is usually something totally unfinished. Personally, I don't post WIPs of any kind, anywhere. I sit around and mess with stuff until I feel it's reasonable, then I post it the "finished" version and let people tear it apart. So, a WIP could be, like, a beta... version 0.4 of a picture. And a non-WIP is version 1.0 or above. Like I could post something at 1.0, and someone could say "hey do this!" and I update the finished version to v1.1!
... I need sleep.