Welcome to my first Sig Tutorial.
Let's get started straight away.
Open up a new canvas in Photoshop and fill it with black.

Now get the render you want to use in this sig and place it in your sig. Duplicate this this render and place around you sig until you have filled it up. Merge these render layers together and then go to Filter -> Blur -> Gaussian Blur - 2.0.
You should have something like this now.

Duplicate this layer and go to Filter -> Sketch -> Chrome and set the Detail to 0 and the smothness to 10. Set this layer to Hard Light and leave at 100% Opacity
You should have soemthing like this now:

Now take out your render again and resize to where you like it and place it in you sig. Get out your favorite smudge brush ( I'm using one I made myself ) and give it a bit of scatter but not to much, and smudge wherever you like so it blends in a bit.
You might have something like this.

Now take out any random render you fancy and place in your sig. You can resize it if you want to. Duplicate it and place randomly around your sig and mess around with the opacity of the layers. 5 layers of this should suffice enough to give some colour.
Hopefully you might have something like this:

Now get out a C4D render you think will fit in with your sig and go along with the flow of it. Now go to Filter -> Distort -> Wave. Click on the randomize button until you have got something you like. Put thsi layer on 90% opacity and place behind your render.
Got something like this?

Create a new layer and get out a soft brush ( 100 px ) and brush in white where you think the lighting should be. for me I put it just between the neck and shoulders because thats the way the light was showing on my render.
After that you might have something similar: