I'm bothered by the large amount of blank space on the right in the default Xenforo header. Are there any add-ons or ideas for putting something useful up there? Useful could mean thumbnails of attachments that have been posted, stuff that uncovers the content on a board, RSS feeds, ads, anything.
There's an ad hook up there where you can put just about anything. I believe it covers everything to the right of the logo
An option would always be to make your theme fixed so you minimize the amount of header whitespace