Well an idea that I like (even though I don't think with my money situation I would do it right now) - but for the user who do give lets say $10 more then their membership gets a "Blue Rook" instead of the normal "white rook". And then maybe make $25 extra a "Red rook".... $40 a "silver rook", and then $75 a "gold rook"

They would have no more privledge then a normal rook, but it will give a user something extra - a status symbol - to show that they have invested to help this site grow.

(note: The $$ amounts and colors would need to be fine tuned, but that is the general idea)