Actually I just had an email from a sponsor that is very unique in that not only have they solved the problem with thumbs they have also made the idea of sponsors having free hosting even more of a reality
Lets say you decide to use all free hosted galleries on your thumb tgp - yeah theres plenty of them out there that do it - and the sponsor hosts the preview thumbs as well on their servers - all you are doing is hot linking them - or one step further - the submitters that want to use this sponsors content can set up their galleries on the sponsors servers with the preview thumbs still hosted there as well
That covers all responsibilities of the TGP as he's not actually publishing anything from his own server - hes just hotlinking everything - basically the sponsor becomes a fusker
Out of reach - nope - I just had one sponsor email that they are setting that up right now