Attached Link: http://www.elite-expressions.com/homepage.html

Graphon, who does those tons and tons of freebies that keep showing in FreeStuff did a set of 12 of what he calls "environments" for poser. These consist of a huge cylinder texture-mapped on the inside with a horizon & sky, matched with a textured ground plane. I start with them any time I'm doing an exterior scene. The link is to his Elite Expressions Site. Tons of stuff there besides the environments, too.