Oh jeez. Yeah, the user you linked to definitely has a massive and headache-inducing sig if you ask me.

Generally I don't bug people about signature size until their sig takes up more than half my screen. At which point I consider it a little bit ridiculous and politely ask them to trim it down.

Try that, for starters?

Edit: As for the thing about "six different disco balls", I guess that depends on how they're displayed. Can you get them to lay next to each other horizontally? If so, probably not a big deal? If they're lying there in a row, vertically, and the image for each is kind of long... that might be a problem. 

Alternatively, you can use sig.grumpybumpers.com to make a signature image rotate - so that every time a page with your sig is loaded, it'll randomly select one image out of a set of images you pick out. That's the best alternative to having a long string of images in one's sig, I think.