Looking at the site layout, the grey is relatively easy on the eyes and runs smoothly. However, the background behind that repeats oddly and is a little obnoxious. Try finding or creating an image that repeats nicely, or is designed as a background for a layout like this.
The images you've selected for identifying threads status, like new posts, no new posts, etc. are a little clunky and don't really tell you what the thread is without constantly having to refer to the key for them.
The header banner at the top is nice, if a little roughshod, but it doesn't blend with the appearance of the site at all. Try making it a little more symmetrical or off balanced to one side, and make it blend a little into the grey forum background.
These are just a few suggestions about the appearance of the site itself. I'm only posting here to give some ideas as to how the site can improve and develop over time.
P.S. Please don't ask me for any help with graphic design. I'm terrible at it.
EDIT:
Boom!
Everything's new, now. Old arguments gone.
Prince_Zora: Please don't double post.