It's just graphics, and the same resolution/filesize graphics at that. It takes no more effort to render than the old snow tileset.
Sadly people think that because they log on and 2000 people are downloading tons of new files... that the new stuff is laggy. Nah, it's laggy because a large playercount is downloading a large amount of updated files. Give it a week or so when the servers aren't being stressed by everyone logging in to check the new stuff out and things will go back to normal.
It's pretty silly that people are blindly hating the update because the server is laggy, as though removing the update is suddenly going to fix everything.