"Some people should not use their pictures for LJ icons. Especially the ugly and fat ones."
Ugly and fat pictures? Or people? I think that's an unclear reference, there.
How about: Some people should not write. Especially the ones with poor grammar.

I actually do have a picture of me as an lj icon (obviously, I'm using it)--because, well, it's a pretty clear representation of me, and I felt a bit weird with the idea that no one would know what I look like.