@firebird: I just like to emphasize that if you would like to do what you like to do then that's the spirit
Hope you just disappear for a moment - don't hesitate to ask, show and tell.
BTW: What program(s) did you use for the poison darts?
Edit:
Oh, almost forgot, as the others pointed out basically everybody can submit/publish on OpenGameArt.org .
But you have to judge yourself if it might be useful for a game.
Concept art and other inspiring art counts as well.
Valueable are of course sets of pieces that can be used together in a game - and again there is no hard rule.
You see, a major difficulty for open source games is to find matching assets/game-art.
So, as Julius pointed out, you may take other's art and extend it - that's one thing: Expanding on what's available.
The other form of contribution is of course to create new art: Extending what's available.
Open source lives by that you do what you like best or do what you need the most.