Wow! That's great. You got me exploring G'mic and I discovered solidify under enhancement. It fills transparency with colour from the cutout.

Looks like all you did was just smudge the background
but looks nice

Solidify is a pretty cool preset. There's also a Script-fu that does this too. Based on a Flaming Pear's plugin by the way. We had a discussion on this a few months ago and the geniuses here came up with these cool tools.

well, the only thing i know how to use on gimp are
Rectangle Select Tool
Fuzy Select Tool
Paths tool(for rendering)
Zoom Tool
Move Tool
Rotate Tool
Scale Tool
Flip Tool
Text Tool
Bucket Fill Tool
Blend Tool(Gradient)
Paintbrush Tool
Eraser Tool
Airbrush Tool
Blur and Sharpen Tool
Smudge Tool(my fav)
Dodge/Burn Tool
Overlay
and Brightness and Congtrast
that's all i know how to use

You really ought to get G'MIC, War Hero - I think you'll like a lot of the effects in there. Play around with the artistic ones - there's a graphic novel effect that might be right up your street.

lylejk - how does the script-fu compare? Is it exactly the same?

Pretty much the same result as I recall but I've not played with either for a while. The Script-fu gives you a layer mask which you may or may not want or can use.

There are many goodies inside GMIC.

Oh, it's a fantastic set of tools! I wouldn't be without it.