CGEmpire is a relatively new site (kinda like www.cgtalk.com) however it's very small, personal, still and very helpful in game//art/music making.

They are having their third contest. One can compete in either form of pixel art, 2D or 3D (all in one division):

Winter Wonderland

They have included sponsors and prizes. The competition was announced 6 Dec , and the deadline is 31 January 07.