This technique will show you how you can get a very interesting background effect pretty easily.
Hi, heres a nice sig/ avatar background image 
Ok, start of with a blank transparent background image of any size u like – im going to do 500×500
Ok, now choose the paint bucket tool, but hold down to choose the gradient tool. Now select the circle shape tool
now choose two colour gradient – with black as one colour. I chose blue. Now set the blend mode to difference at 100% opacity. Now start making random shapes, just go wild with the tool. The more u do the better it looks.
