God no. Avatars are only acceptable when they are done tastefully. I've been on certain boards where members are allowed these obnoxiously large avatars that screw up the table formatting in unacceptably awful ways. In most cases, the table stretches itself far off to the right of my browser window, forcing me to scroll left and right when I actually want to read their damn message. No. Terrible. The only use of avatars is to provide a visual guide for the quality of your post. If your avatar goes farther down the screen than the text of your post, just hit the Back button and save us some time.
And don't even get me started on images in signatures. Most of them are so damaging to the eyes it's unbelievable. Taste, people, taste! God, if I have to look at one more Frankenstein-image, formed by smashing together a zillion unrelated screencaps from some crappy anime, I will scream. See, this is why piracy is bad. It allows these people to obtain Photoshop when they normally wouldn't have been able to, which allows them to assault our eyes with these monstrosities.
(- Steve -)