lol i made it on 2mins -.-
With an non-legit copy of Photoshop, using
- layer adjustment -> color gradient
- Pencil Brush Leafs ( Photoshop standard )
- Pencil Brush Dots ( Photoshop standard )
- Filter -> Clouds -> spread
However, i don't want to blame you boy but seriously, if you want to make art ( or a computer game ) create a deviantart account, post your works over the next two - three years and become a good artist. Then go to university and get a good certificate. This may take two or four years depending on the stuff you want to do. In the meanwhile, you sure have worked as freelancer programmer and / or designer and made some experience and contacts to people from the business.