These sort of images are very popular on most stock sites.
and the downloads they recieve for such a simple concept is phenomenal. 
But what if the sky where you live is always dull and grey?
What if the grass is never as green and lush as they appear in the photographs?
The answer?
Follow the direction of this really cool online photoshop tutorial
Grass and sky tutorial
and watch the downloads flood down.
Here's an example of how it could look-
(I'm off to make mine now) ;-)
and here it is.-
P.S.- if you find this article useful then please click the useful button above. Thanks