Boone covers and a quick way to create great backgrounds with After Effects Shape Layers.
The more you use Ae, the better your work becomes. You can create vector artwork with ease and get creative by using shape layers! One of these tools is called “repeater addition” which allows for creating backgrounds quickly without having too many details in one area.
The whole system is also a great way to make patterns (be it for background or something else). Have a look at one of Evan Abram’s tutorials that explored methods for designing and animating infinitely seamless backgrounds with his tools like Motion Tile, RepeTile and HexTiles.