Are you arty-farty?
Well you know about arty - the adjective of art but how about farty?
Well, if you'll excuse me, it's a noise and smell made from the lower part of the body which is highly amusing to small boys!
Therefore, to call someone arty-farty is a pejorative term.
It means arty but in a pretentious way. Generally, there can be few more pretentious people than art critics.
Here is a delicious speech about the art critic read by Peter O'Toole from the beautiful Ratatouille film. I don't care if it's pretentious, I love it!