This tutorial will show you how to make a basic fall out sig, the rest you will need to customize.
First start off my opening a new file and make it the size you want the background to be, then make your background, i made one like this

now save your background as a *JPEG*

JPEG JPEG JPEG
now open the JPEG

press CTRL+A to select the canvas
copy thr BG
Now open a new file, keeping the width the same but making the heigth bigger (you dont have to use my size)

Now paste on the background, and drag it all the way down or to where ever depending on how you want the sig. Then paste the render over it and move it around however you want
the last part is to go to your forums home page, and take a screen shot of it (print screen) paste that into photoshop and eyedrop the color where the sigs pop up, paintbucket this as the BG.
*important*
dont edit the JPEG with color balances or anything, once you save the JPEG you are done