Visually a very nice clean design with the colours all complementing each other nicely. Maybe my next suggestion is preference driven but I would have added a indent bevel effect under the orb. As I stated this would have been one of my personal preferences.
I really like the logo and how you intergrated the login and search feature into it. top marks for placement of these two features.
However, The vbulletin stock images which haven't been replaced (sub forum status icons) could do with being replaced, this shouldn't pose much of a problem for you judging by your design (which is very nice).
Other stock vbulletin images which I think you should replace for something custom which would give this style a more complete look would be the
navbits_start.gif, navbits_finallink.gif aswell as the
stats and
who's online and
birthday icons. this at least would complete the index page (forum).
I would also recommended changing the
Threadmarkers in the forum display page. Custom always looks visually better not to mention something designed that complements the theme looks visually more appealing and consistent which is always a good thing.
Overall. Nice theme with a few areas left incomplete which would take an hour out of your time to rectify.
Nice work.