An easy way to make text or a render pop out of the image is by making sure the background is transparent. Create your sig on the transparent background, and when you are ready to add the render or text that needs popped out, you simply increase the cavas size, which leaves the sig itself in place, but creates extra transparent space for you to work with.
So, if you wanted a sig that was 400 x 200, you would create a new transparent canvas to work on using 400 x 200, create the sig - then say you wanted the text above the sig, you would increase the canvas height by say 10-20 pxl, depending on the size of the text, which would leave the top portion of the sig transparent, and keep the rest of it as it was.
Save the sig as a PNG, and it will be transparent.
EDIT - There are other ways, probably easier ways, so I'm sure someone will come along and tell you a better way.
Last edited by M.C; 09-01-2009 at 02:12 AM.