In my opinion there is only one exception I see and that is if you purchased the same exact item yourself. But even then, you should probably PM the filler to clarify that you purchased it.
I've seen people post items I originally filled. If you're not posting it soon enough after the original fill (not a day or two, more like two weeks or longer) then that is kinda on you for not posting it.
But posting an asset from someone else's fill... that's a dumb dickhead move because as @ulysses said, you'll probably get banned.