My guess is that if you use a sponsor's image for a header, it better be clickable and take the surfer to that sponsor... unless that is the only sponsor you use for the site.
http://www.cuteasiangals.com/ use sponsor content on loan from a sponsor, but it also links to the sponsor.
http://www.sexygothgirl.com/ is the same design, different sponsor.
A different design which I think is cool beyond fucking belief and a total bastardization of some poor theme-writers intent (You gotta love GPL) is the computer-browser version of
http://www.teenage-sex.mobi/ . It uses retouched, cropped and combined banner ads as a sliding header, but once again since it is technically sponsor content, it all is linked to the sponsor's different sites.