I usually find artists on Deviant Art but I ran across this site and thought I'd give it a try.
I'm in the final phase of development for an isometric pixel art fantasy RPG to be released on Windows PCs, tablets, and phone. I'm looking for a talented pixel artist to create isometric character sprites.
My previous games are similarly themed and have received over 2 million downloads; I expect this game to be more popular than any of those.
I'm looking for an artist who can create isometric pixel art characters (similar to the style of the original Final Fantasy Tactics). Size is 32x48. Each character sheet is 8 frames and I need about 20 sheets total and I'll pay an average of $50 per sheet but that will vary depending on your quality and turn around time. Total payout would be about $1000 via PayPal. I pay half up front or as each sprite is completed.
Your artwork looks good enough that I think you could make these. If you are interested I'll get you the details and we can start right away. Email me at nathandarst@gmail.com for details.
I know a few people have done compssions before on OGA, I would also check out the irc channel #opengameart on freenode
=======
Full Steam Ahead! o/ <-- little ascii fist in the air holding a debugging hammer.
http://wayofthepixel.net/index.php?board=6.0
http://www.pixeljoint.com/forum/forum_topics.asp?FID=11
I don't know if he is taking commissions or what his rates are, but I know Tim Jonsson has created high quality art like you're asking for.
Tim Jonsson's DeviantArt: http://timjonsson.deviantart.com/
Isometric TRPG sprites: https://github.com/saniv/free-game-art/tree/master/isometric/spell-of-mastery
Walking animation example: https://github.com/saniv/free-game-art/blob/master/isometric/spell-of-mastery/tiles/Unit/Animation%20Examples/greenhood_walk_front_left.gif