No plasma, I used a pattern (random, but it should be a bit coloured), filled the bump map with it and made * Filter-Artistic-Cubism *
With this Bump map I bumped the gray layer, made a second gray layer and bumped it with the first bump layer.
Then I made the same thing with another bump map but instead of Cubism I used * Filter-Artistic-Canvas * and a little gaussian blur.
(Since I have the German Gimp Version the names of the actions may or may not be the real Gimp names, I just translated them)
And the map is on hold until next week, I'm away for the weekend.