Ragnar, I might be able to add GPL as an accepted format. But the really slick way to do it, would be to have a zip file which contains the GPL file, and then some kind of image, that displays the swatches.
See the attached file. I saved that from an old IF topic. I't a zip file with GPL, PDF and PNG files. I don't think we necessarily need PDF. I think the author included it because it's more "universal" than SVG. I think PNG should be sufficient for us though.... I can't think of any reason why a vector file would be needed, except just for completeness.
I'm working on the gallery, at the moment, trying to get the user galleries to have a thumbnail on the front page, like all the other categories. But after I finish with that, I'll test uploading a zip file. It is an accepted format, and should work, it's just that I've never tried it.
Probably will need to use the image (PNG) for the thumbnail. But if you're willing to go that far (making a zip file for palettes) a Palettes album would be an awesome addition to the gallery, and entirely do-able! Might even inspire others to make some

I might actually have some of your palette files. I'll have a look, later today.
Janne, yep, that's the manual's info.