1. Can you add something about constructive commentary? I think that people coming in and crapping all over someone else's work is a pretty constant problem. Usually from people who post no work of their own.
On the other hand, some people who don't post their own work might not feel free to comment. Everyone should be encouraged to add their opinions, whether they contribute artwork or not.
2. How about a statement about what media and subjects are acceptable, with some examples? I know that everything Trek is allowed, but some people might think, on the basis of what they see posted, that only 3-D renders of starships or Photoshop pics are okay but that sensitively rendered pencil sketches of crew members, manga-style comics, modified action figures, and Lego sculptures are not.
3. A problem I've noticed is threads breaking down because of arguments about the content/subject of the work rather than the execution. Most of these center around issues of "canon." I remember there was some trouble about what should be left in the tech forum and what is acceptable in the art forum.
4. Finally, I'd like to belatedly second the suggestion of www.photobucket.com
as a easy to use free hosting service. This site actually encourages inline images. I use it all the time myself.