It depends on much time you want to invest. For the most control you could convert the art into paths in illustrator, bring the paths into AE and apply trim paths. This way you can control which paths draw on when & how fast. AE also has an auto trace effect in the layer menu which crates masks over images. You can then apply a stroke effect set to "all masks". This is a much faster approach but will sacrifice a certain amount of control.
I'm sort of a beginner and just learned about the auto trace feature in AE. I've been fooling around with it in my spare time.
here's one tutorial on it. There are lots. Just search Auto trace in After Effects on Youtube
Hey sorry I took so long to get back to you get extremely side tracked!! Thanks you for your answer I will look into it. I now know the bull brief of this work so will post a new message as I need to hire someone to do this for me as its way out of my depth!
After Effects is the wrong tool for creating an animated web background. AE makes video. You'll want to look into using scripting to animate vectors in HTML5.