An interesting mixture to “pay what you want” and “ransom funding” has recently surfaced with the Open Bundle:
You can buy all the offered game art and use them under the CC-by license and if the total threshold is reached (10k, 1 day remaining, 9.3k already pledged) all the game art (2d sprites and music) will be officially released under the CC0. A split of the funds is btw. shared with the EFF and Creative Commons.
Do you want to host your own “public domain ransom”?
I’d love to help you! Email me at firstname.lastname@example.org