Well the way I've done it (for smaller teams) is to split the profits equally if everyone is doing similar amounts of work, or as close to equal as possible. So for one game that I made, the two people who funded the studio and did all of the art, main design work, and programming both took a 40% cut, and then the third person who did character animations and co-developed levels got 20%. I would give a good artist an equal cut to the programmer, as long as the amount of work needed to do is roughly the same. It sounds like you need a lot of assets, so I'd offer a more equal split of the profits if I were in your position. If you did all of the design work and programming, then a single artist (rather than three different ones) should get get at least 35% of the profits, in my opinion. Just my two cents. :)