Ok, I m going to try and explain this VERY Simply. Here it goes:

Today we will be making a Sig on GIMP. The outcome will look something like this:



First Pick out what Render you want to use. Now Open a new Canvas, any size...I used 420x121. Now take one of your favorite Brushes, and brush around with it (But use A color that matches your render.) Now I Had this:



Now make a new layer and name it "Burn Layer" and then put it on top of your background. Now fill it in with your original color so it looks something like this:



Now Change The Mode Of "Burn Layer" To Burn. It should now look like this:



Now put in your render so it looks something like this:



Now duplicate that layer twice. Now Select The duplicate on top of your original render and change it's mode to Overlay, bot it looks something like this:



Now on the other duplicate, select it, go to Filters > Blue > Gaussian Blur. Play with the settings until you like it. Then set that layer to an Overlay so it looks like this:



Now you are done with the render part. Now go to Filters > Text > Free Type. then choose a font and color. then insert what text you want. Mine looked like this now:



Now You are done. You Can Add A Border In, Add Lighting or whatever you want now. (For Indepth Tutorial on How To Make Borders, See My Border Making Tutorial **COMING SOON**)

This is my final outcome:



-Enjoy!

Other Results:

(I'll Add Them As People Post Them!)

---