The Forum looks pretty cool but like Sunil said, the header looks a little out of focus, and why don't you try to create a header with that folder color, just a suggestion...
The image is a JPG. If you make it a PNG, since your banner is only black and red, there's no need to worry about space, as it'll still only be around 10KB big the most.
I would say get yourself a slightly more colourful header. Maybe put some photography in it. I would then change the black background, I wouldn't really expect photography forums to be black, I would have expected it to be maybe a light blue or something.