Looks nice, but I've got some suggestions...
First, while it does look nice right now, the background image doesn't exactly match the table colors. It still looks good as it is, so it's not really necessary... but you might want to experiment with a background image that better matches the tables.
Second, I wouldn't suggest having the static (watermark) background, especially with all the other page elements you are using. WIth normal backgrounds, the page is drawn once and you scroll up and down and it all works great. However with static bgs, the page has to be redrawn every time you scroll. On plain text, it works fine. But you have so many more tables and images and animations, that the scrolling goes REALLY slow because so many elements have to get redrawn. I couldn't scroll around on the UBB since you have blocked off guest users, but it was really apparent on your main page.
Finally, I would suggest that you update your version of UBB. Since you are choosing to go with the 6.0 beta, it is suggested that you keep your version current to keep up with the latest bug fixes and stuff like that.
Aside from that, it looks nice. Nice choice of colors and stuff, for the table at least. Looks pretty good!
---Skorpion
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