Licensing art

[kiriska.livejournal.com]

Okay. Looking for advice about licensing commissioned art to the commissioner commercial use.

So I am potentially going to be doing a lot of art for a guy making a tabletop RPG -- he'll be using all of the art in a guidebook that will eventually be for sale. Since this is something a lot of people want to do and since I don't know enough about the project to really form an opinion about how likely it is to be commercially successful, I would rather not deal with royalty payments that may or may not ever happen and would prefer a lump sum one-time licensing fee per image.

The guy pointed out that a flat-rate fee per image (in addition to the cost of the commission itself) would add up quickly for him, since he would need dozens and dozens of images. I understand this, and I understand that this is a very indie project and that he isn't a big business with lots of funds. I do want to be as reasonable and fair to him as possible, but I want to be fair to myself as well, and in the event that this guidebook is wildly successful, I don't want to have given away usage of the art for little more than what the art itself cost.

So I'm not really sure what would be a good compromise. I was thinking about percentages, like maybe a 5% licensing fee on top of the cost of each image, though some of the smaller images would be something like $20, so 5% is only a dollar, which seems.. silly? I don't know.

Advice?