Unfortunately, there are artists like Wyman that seem to be blithely unaware of how this can improve the marketing of their commissions.
His art is already selling at relatively high prices, so maybe he doesn't mind… :-
perhaps he thinks that by posting some Hyper-large images people won't buy any his works, because they can print them anywhere they want xD
…and there is that reason too. ;D
RICK BURCHETT ORIGINAL ART from SHE HULK 10
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170325919598