Solid background

[akovia]

Hey George,
Not 100% sure what you are seeking with your explanation but I made some modifications to your xcf.

1. I cleaned up the border so the edges are not so rough by using a path.
   
2. I removed the background from your running man so you can use any color as a background for the entire image.
   
3. I made a background layer that is the the same extents as the border.
   

This gives something like this..