Create Color Palettes for GIMP

How can I create a wallpaper that reflects my color scheme?

Assuming the color scheme is available to you, save it in rrr ggg bbb format to a plain text file with a short header. Example for Gruvbox:

GIMP Palette
Name: gruvbox-test
Columns: 5
#
142 192 124
69 133 136
215 153 33
204 36 29
60 56 54

Save that file in ~/.config/GIMP/*/palettes with a .gpl extension.

Now fire up GIMP, open some image, then go to

Image => Mode => Indexed... => Use custom palette

Your new palette should show up as "gruvbox-test".

Applied with dithering it looks like this:

gruvbox palette image

This is a fairly good result (but by no means the best). Images might require massaging before applying the palette (contrast, saturation etc.).

This palette has only 5 colors; Gruvbox has more to offer but larger palettes don't necessary give better results.