Please add some information about payment for the artist to your post. If this project is not paid, or if it is revenue share, you can reqest that a moderator move it to the Unpaid section by Reporting the post.
Some other information that might be helpful to prospective artist:
Are you looking for someone to replicate the Pokemon sprite style, or do you want an original style?
Are you using existing Pokemon, or creating new ones? Or, more to the point, will the artist need to design any Pokemon or other characters, or will they be working with existing designs?
How big are the sprites?
How many different sprites do you expect to need?
Is any animation involved? If so, what kinds and how much?
Do you need any environment artwork? If so, illustrations (like the ones shown in some Pokemon games when entering a new area), tiles, both, something else?
Are you imposing any deadlines on the work, and if so, what are they?