I run a site that sells content (textures, models, sprites, etc) to indie game developers.  I'm thinking about hiring (contracting) some pixel artists to make content for resale on my site.  I would certainly be OK with profit sharing, too.  My sprite section is pretty empty so far.  I've done some game development and texture art, but I've never worked with pixel art, so I'm really out of my element.  Here are my questions:

1) What are some example projects you've done and how much were you paid?  (This will help me figure out how large the projects I choose should be.)
2) In your opinion, what are the most popular types of sprite packs?  For example, platformer?  Isometric fantasy?  Top down space shooter? (Sorry if I sound dumb here!)
3) For mobile games, what is the most popular sprite size?
4) I'm very concerned about proof of authenticity.  If I do hire someone for contract work, what's the best way to ensure their work is original?
5) I've seen sprites (like these: http://www.molotov.nu/Graphics/Angband/Monsters/dg_monster232.gif) that seem to be variants on a theme.  Should I be looking to hire someone to create a mix-and-match sprite system, so that it's easy to combine sprite pieces to build custom sprites?  Or, is that not a good idea?

Thanks!  Any advice would be much appreciated.

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Bret
http://www.gamebeep.com