Ahh yes, the Avenger style. One of the better executed dark styles.
Header looking good, avoiding the garishness and luridness we usually see with gaming sites. Tasteful.
You have it nice and svelte with only 285kb of page load on the browser. Good to see. This will be friendly with your members.
You have a missing, mis-named or mis-spelled image call, here: (404 not found error)
HTML Code:
URL: http://www.mistviper.com/forum/images/avenger_blue/gradients/gradient-grey-down.png
Postbit looks nice and clean, the extras aren't grating at all.
I would install BoP5's Xenforo Breadcrumb, and definitely would get Ozzy's advanced footer, to really pimp this out some without adding any significant extra load. I have those on
my site here for your viewing enjoyment.
Also you're not leveraging browser cache of static assets. This is a easy fix in .htaccess.
Overall, nicely done. Refreshing to see a vBulletin that isn't loaded down with 2 megabytes of heavy imaging. People can find and go to, what they're looking for. Uncluttered.
Nice job.