Revenue ideas to add?

I would like to see one thing added.  I would like to sell advertising links in a users signature.  Even if its just x number of posts or week(s), months or yearly.  I know there are programs out their like google but I hate jumping though their hoops.

To allow a user post a link on there signature with paypal is a simple way for a forum to get some supporting revenue. 

If not selling links then maybe a pay to enter a forum.