Actually, if you have a simple graphics editor, you can make just about any avatar or sig that you want. But it is nice to have places to download from.
Reminder, please check out this thread about sigs, avatars, and user titles. It may help while you're looking for new ones.
Again, I make my own tag lines. (like my current ones)
How ever, if i do see a movie quote or song lyrics that I like, I will note down.
Eg. "Agony or ecstasy? Even after 2,000 years the rush of a kill still make me feel a good death was worth living for." - Os, Invincible