[SaintDog]

With the current setup, everything resides on the same server and while the loads are not high by any means, there's room for improvement and seperating that which gains the most traffic is the best starting point. In this case, it's the images and attachments.

The other static files simply aren't hit enough, or even used as much to warrant moving them to their own server. It's kind of the opposite end of the spectrum.

Most people use vBulletin as a community software, in this case, more of a download and image manager.