Wondering how to make backgrounds?

Alright heres the deal, i would like to learn how to make those sweet backgrounds but i can never find the right programs. i have used photoshop several times but i want the backgrounds for like a desktop with mountians 3d abstract things likes spheres and streaks of paint and i don't think you can that with photoshop. I'm basically asking you guys what programs i need to make 3d backgrounds.