OK- here are all our solar systems planets in flat texture maps that can be put on  spheres.

http://planetpixelemporium.com/planets.html

And here is a link to my old planet pack for Poser if your just makeing still pictures.(20 plus MB)

http://a-lot-of-jigsaws.com/other downloads/Geo's_Planet_combo_Pack.zip

Also in the store I have 2 background packs now available :)
http://market.renderosity.com/mod/bcs/index.php?vendor=25852

And lastly, just tonight I posted a link in the contest forum that has a monthly contest with a 50$ first prize for space pictures (see rules)
http://www.diardsoftware.com/

Hope this helps :)
Geo