Is there a ceiling on the size to which an image may be upscaled?

One wrinkle a vandal figured out today was altering the image markup on [[en:User:Hephaestos]] to produce a massive image. Done prolifically, I figure there's some potential both to DOS the server that does the scaling, and to similarly slow visitors' browsers.

I can't see much reason to allow scaling of images to beyond a few thousand pixels.

FIn