Ok, sense you asked for advice in a message, I'll gladly help you out. 
The background is great, but I do know a few things that could help you out.
And
REFERENCES are big helps! I'll post a few image URLs on clouds, and skies, and grass and such. :3
First, one thing: the clouds are awesome, but they are missing a bit of color.
If you look at this picture:
CLICK HEREYou can see that they have greys and white.
Second, the sky is one color, which is a greenish-blue. And you want a light blue. But you don't want just one color. Try to mix colors and fade colors.
Like in this picture:
CLICK HEREYou see it darker at the top and fading in lighter colors as it goes down.
Third, the grass. It looks good, with the different colors, but I'd say it needs to look more pointy to look like grass.
This picture isn't real but it could help with the pointy look with your grass:
CLICK HEREAnd this picture is real:
CLICK HEREIn the real grass you can see, the closet grass in more shaded, and further, it's more light.
Did this help you?