I recently came across the fantastic website Seven Wonders in the UK.
Go take a look at the wonderfulness here - http://www.seven-wonders.co.uk/index.html
There are hundreds and hundreds (nee thousands) of pages of paper characters available. These are all in the style of the classic Steve Jackson Games cardboard heroes.
There are all sorts of genres, with lots and lots of super heroes, all sorts of gaming genres (including 160 pages of pulp characters), heavy on the fantasy and science fiction (lots - classic, post apocalypse, etc), horror and so forth.
|A sample sheet of Steampunk characters, as an example.|
The art is from (according to the FAQ) scanned physical sources. The site owner is completely non-profit, and offers to remove any art that is challenged by a copyright owner.
Is there a down side? The only one I can imagine is that you have to download the images through a download site called RapidShare, but in the FAQ, the site owner (and creator of the figures) says that a redesign is in the works.
The site operates by donations - if you use any of these - donate something. It is worth it!