There is, the same way we create them. You need at least Inkscape and ImageMagick to make the stuff happen.
This placeholder page in the wiki won't get you far, but it exists:
http://runningwithrifles.gamepedia.com/ ... e_new_mapsJackMayol has been intending to re-start with a map making tutorial at some point, but unfortunately it keeps getting delayed because of other things to do to advance the game development.
A few years ago a map making contest was held
viewtopic.php?f=2&t=493, it might have some hints too, but most of it is probably outdated by now.