I just now saw your email with the questions. The mountains have snow at the tops - then they are mostly green from trees - with many rock cliffs visible. See picture at:
http://www.panoramio.com/photo/4885716We don't have Saguaro type cactus like you put in the picture - but we do have prickly pear cactus and mesquite trees if you could put some of those in for some depth - that was a good idea.
The sign bigger and with a shadow is good - but it is a bit tall and conflicting with the mountain top - can you shorten a bit.
The riders: I like what you did depicting the gear. Much better. If you can make them in a more aggressive stance that would be great. Can you make them white people instead of black people? Could you make their shirts white, shorts black, girls hair blonde, their backpacks black, their skin a tan or flesh color, helmets black on the girl and red on the guy?
After that - i am about out of ideas - but would welcome any more ideas from you. Thanks again.