If you are having trouble coming up with artist nominees, I encourage you to browse the Locus Index of 2010 Covers.
I'm personally planning to nominate Kinuko Y. Craft, Julie Dillon, Andrey Lazarev, John Picacio and Tom Kidd for the work they've done in the past year. I particularly liked Dillon and Lazarev's covers for Clarksworld; those folks are doing an outstanding job recruiting artists for their covers.