I quite like the rich textured browns you've used for the forum but the way you have implemented the whole colour usage thing into the style looks far too overwhelming. Break the theme out with other colours (yellows, touches of white) and maybe another colour. Work on the alt1 and alt2 areas so the compliment one another rather than dominating the landscape. When using vbulletin stock and implenting colour shifts (with the hue and sat/colour balance) is fine, if... the actual image is broken down to it's base layers which the vbulletin images aren't (referring to the forum status icons). I would go with something custom, something that you can easily manage and implement colour shifts on specific layers which need that colour shift implemented too.
I would also tone down on the textured backgrounds a little or at the very least don't make it so dominant.
Also, If you look at the
whats going on area or more importantly, the icons which reside in this area you'll see a nice white matte edge which can easily be rectified by (pending you want to use the vbulletin stock) save it in the correct colour, the colour of the background it's being applied onto.
Overall, colours are nice but implemented poorly and images saved incorrectly. All easily corrected providing you spend the time and effort on the styles and images and of course the colour implementation.