Yes, that happens when the game can't find the graphics and/or the map file.
This probably is a problem on the game's end. I don't think there is a fix for it without me editing the source code which can't be done after submission.
But for future reference what linux distro are you running? (As it does seem to work on debian)
Sorry to hear that, I haven't had time to debug for other platforms it might be a problem with how file paths work on linux, make sure the 'res' directory is placed next to the game's jar file. You could also launch the game with the command: (this will show an error log if there is any)
