my backgrounds consists of about 3 brushes 2 are blended in i will do a brush that stands out like arcane circles, tribal tattoos stuff like that then merge all of it togather when ready then open the render then go back to the main gimp area and open a new file with the background transparent i do it like 400x400 then copy the sig and paste it im the big transparent box, then move it around till it's a little close to the bottom but not all the way down. Then anchor that layer then go to your render and copy that and past it on the sig then move it around and let it stick out any way you want it then when it's all good anchor that layer and then your done, it's hard to explain but you will get it.