So currently I'm working on these: for shutterstock.com. If I had all the time in the world I'd do so many and earn so many quarters!
But really - how do you, as an artist, make money on art that's just sitting there. Say you had a freelance project...or were even just working on your own stuff - how do you make money when it's all said and done? One way I've just discovered is to put your work up on photography sites under the illustration section. It's making a passive art portfolio - you have art that's just sitting on your computer (vector images work the best), and it's just collecting dust...if they're good images or logos or icons, you can start making money with them...all you have to do is upload them to Shutterstock.com - I'm working on getting approved to be on other similar sites, but this is the first one. You get 25 cents a download - which may seem like nothing, but it's better than what the picture was doing for you earlier.
If you decide to try it - http://submit.shutterstock.com/?ref=325258
my referal number is 325258 (if you cared). Anyway - I would keep talking, but I'm going to go back to making money. One quarter at a time.