Thanks a lot :)
Did you also move your attachments and avatars to another server or just the style-images?

Also the attachments and avatars. You need to specify a filepath location for the attachments & avatars, and have the image server point there. Also modify the url to the image's server.

If they are two physically distinct servers you'll need something like nfs to keep the avatar & attachments & profile pics synchronized.

Yes I could change the avatar-path in the AdminCP to an external server and rsync the avatar-directory... But what about uploading? If someone wants to upload a new avatar, vBulletin will most probably try to write to the directory which is an external URL in this case. Is vBulletin able to write images to an external server without modifying the vB-Core-Files?

Have you experience with running 2 http servers on the same box, one for images? Just curious to see what if any performance that might bring about to have one caching and the other dynamic on the same box...

well ..
if there 2 physically different server..one for vb itself
and 2nd for only avtar/profile pic/sigs/attachment

how to do it?