I don't know much about licensing content, but it would seem logical to me that given the way that sites are marketed these days, one could go to the licensor and try to negotiate rights to produce screencaps from retro content... for that matter, if the licensors themselves spent a few bucks and made some nice screencaps and had them cleaned up by a good retoucher, I'd think that would be worth a premium amount in licensing fees.

Of course, that's operating under the assumption that the people licensing the content are logical people who understand business, which might be a questionable assumption