http://vector.tutsplus.com/tutorials/illustration/how-to-create-a-seamless-bird-pattern-with-retro-touch-in-illustrator/

In this tutorial you will learn how to create a series of minimalist and stylized birds and create a seamless pattern from them. The tutorial is aimed at users of Adobe Illustrator CS5 and below, since in CS6 creating patterns has become easier and more intuitive. In the second part we will then use this pattern for what could be a poster background and apply some effects to give it a retro look.