How to find an artist for a prototype game?

first,
1.If you like a certain style of a game, there should be an "Artist" credit somewhere. (like at the bottom of "trading card game" cards)
Then just look 'em up online and inquire about prices and such.
People who do art for this type of stuff usually like to have a size, complexity, and deadline in the inquiry to give you a good quote.
Check out Barnes and Noble for a book titled "Graphic Artist Guild: handbook of pricing and ethical guidelines" to get a general pricing, so you know what to expect.
Sometimes you have to track Artists down through facebook and such.

and 2.
Usually if you are approaching a company (like say, wizards of the coast)
they have been doing this stuff for a while, and would look at a game and say for example: "robots are hot right now, lets make this about robots!"
in this instance, if you had completed art, you would be out the money you spent on the artwork that wont go to the final print.

all-in-all:
if you want to complete the art with an artist you choose, self produce.
if you want it to just sell... then leave the prototype rough enough that you aren't bending over backwards burning candlelight.

http://www.indie-rpgs.com/forum/index.php?topic=17039.15

And, if memory serves, when I was looking for art for my game, I went to www.deviantart.com (I think there was a call for artists forum, though I can't seem to find it right now). There are actually a few forums for struggling illustrators who would probably love to do a freelance job like this (though make sure you negotiate price & details up front).

I see this question asked a lot, and the actual question I think you should be asking is "who will do my art for free?"

The answer is that you get what you pay for.

Either you can pay in time (and blood, toil, tears, and sweat), and learn the craft on your own, or you can put out a call for artists for a given price, and see who responds.

I don't often see good artists hooking up for free in order to do art on a prototype game. A game that's going to production, maybe... because then they can get their name on something... but a prototype game that may never see the market? Put yourself in an artist's shoes. Would you work for free?

So, either design the prototype with stock art (read Girl Genius and scam some art from there for your proto if you have to), or do stick drawings and send that to the publisher. The publisher will pay for art if your game is picked up.

For now, concentrate on making a good game.

This is true enough. People tend to forget that professional artists need to eat and pay rent too, and have unreasonable expectations of what high-quality artwork costs. That said, you can probably find someone willing to do something reasonable for less than $70/hr. because of the nature of the project. As a graphic designer, I'd be charging that much for boring corporate clients, but because I want to work in indie computer games, I usually ask more like $25-30, since I know that indie devs just can't afford regular freelance rates.

You can also go looking on sites like deviantart.com, where you'll find more amateur/aspiring artists, who might be willing to do some work for cheap, or even just for the credit/experience/portfolio piece. Alternately, you may be able to find people who have existing art similar to what you're looking for, and get ask them for the rights to use it cheaply or for free.

Matt Orsman with Mirthquake.net

Is a fantastic artist who understands packaging and prototyping

Wes