And there probably is in the 99% of the game we haven't seen.
Very good point and I agree. A lot of the screens were taken near Throat of the World.
But we've seen some pretty diverse areas so far.
Like these:
http://skyrimguild.com/wp-content/uploads/2011/02/SkyrimTrailer2.jpg
http://skyrimguild.com/wp-content/uploads/2011/02/SkyrimTrailer5.jpg
http://cdnstatic.gamesas.com/akqacms/files/tes/screenshots/LakeWaterfall_wLegal.jpg
http://cdnstatic.gamesas.com/akqacms/files/tes/screenshots/MountainForestPath.jpg
http://skyrimguild.com/wp-content/uploads/2011/02/SkyrimTrailer6.jpg
http://attackofthefanboy.com/wp-content/gallery/elder-scrolls-v-trailer/elder_scrolls_v_skyrim_screenshots-1.jpg
http://dl.maximumpc.com/galleries/Skyrim/Skryim-Trailer-anolysis-4-Forest-Statue-Head.jpg
http://www.mouseandboard.com/wp-content/uploads/2011/02/skyrim32.jpg
I'm fairly sure, but of course not 100%, that some (not all I think) of these were taken in seperate places. We can even see the ocean in this one: http://skyrimguild.com/wp-content/uploads/2011/02/SkyrimTrailer3.jpg
Still, I think the trees could vary more even in the places we've seen so far, despite them not showing the entire game. Kinda like this: http://planetelderscrolls.gamespy.com/fms/Image.php?id=101650