(tl;dr: if someone can give me SVG or layered XCF source for the OpenJK icon, I'll try fixing this myself.)

If you have all the flavours of OpenJK installed, they aren't distinguishable at a glance because there's only one icon, particularly with GNOME Shell's bad habit of truncating app names:

The original games solved this by having a different icon with multiple lightsabers for MP mode.

Return to Castle Wolfenstein, which has the same "separate engine for SP/MP" issue, has traditionally got around this by having different coloured icons, and iortcw (analogous to ioquake3/OpenJK) does the same for its redrawn icon. For the Debian packaging, I also made it more obvious which colour was multiplayer by editing that icon to have smaller, alpha-blended copies:

Does someone have a source file for the OpenJK icon, like a SVG or layered GIMP/Photoshop file? I'd like to try doing a similar modification for that. Perhaps JK2/SP could keep the blue-on-black (or get more blue) to be reminiscent of its box art, JA/SP could have a more teal/green version to be reminiscent of its box art, and JA/MP could have multiple lightsabers shown?