It's not a totally foreign thing for MMOs to beef up their servers if required WoW has done it as have others if I'm not mistaken. I think a few people misunderstand what the servers actually do though, they wont give us better graphics for one that's entirely a client based issue on our end and them designing for the lowest common denominator to run the game at a respectable visual level.

Why they don't give us options is beyond me though, a high resolution texture pack would not tax the servers as far as I am aware it would all be on our machines end to handle the graphical processing as all the files are located locally and not server side.