The easiest thing to do would be to go to the technical support board, post the picture, and ask someone to reduce it for you. They'll reduce it and maybe put it as your avatar for you if you ask them.
well I've made mine
and I made my brando clipart small too(it was this huge pic! lol)
all you do is go to paint...and then shrink it to the size limits(avators are 50 by 50 I think..at least mine is ) and then go and add it as your avator