A GIMP tutorial for when i didn't have photoshop, about a year ago!
Here is a gimp tutorial. I will teach you how to make this
First pick a render. You can get some from
Planet Renders
For this tutoial i will use this render

To use it don't copy and paste it save it. This is to use it as a render not a background.
Open Gimp.
Then go to File-New and create a background size 400 wide and 120 high. This is the best size (in my opinion) for creating a sig.
Then open the render as a layer. Go to file-open as layer (or Ctrl-Alt-O)
It will have this in the layers dialog
While the linkrender is highlighted as above click copy. This is for a later step
Click on the eye on the linkrender to make it invisible.
Then click on the background layer.
Paste the link render. And keep on pasting it and moving it untill the whole canvass is covered. As so

Then anchor the Pasted Layer, by clicking on the anchor in the layer dialog.
Click on Filters-Noise-pick
Max out both the sliders and click new seed button.
It should look something like this

After that, click Filters-blur-motion blur.
Set the setting like this

And you should get something similar to this

Make the Linkrender layer visible again, by clicking where the eye was on the layer dialog.
Change the mode to hardlight. The mode is located here-

After this it is for the text.
Click on the text on the main gimp dialog.
Pick a font you would like. I have chosen The streetwriter font which i got off
www.dafont.com
Make the colour of the text white and Write your wanted text. I have chosen Fraz.
It will look like this

Then set the layer mode to Grain merge
Now for the border.
Make sure you have Black As your main colour.
Create a new layer.Name it border.Make sure the layer is on top.Like this

Go to Select-All (or Ctrl-A)
Then Edit-Stroke selection
Then have line width as 10.
After that make your main colour a dark green(because most of mine is dark green, Yours could be different)
Edit-Stroke selection again This time make the line width 5.
This is how it should look-

You are finished. Well Done.
Please post your results