If you want to build the maps directly in Roll20, try using tiles. You can get some spaceship / sci-fi tiles on the Marketplace of Roll20 for a small cost for a set. <a href="https://marketplace.roll20.net/browse/search/space" rel="nofollow">https://marketplace.roll20.net/browse/search/space</a>... If you want to build maps outside Roll20 and then save it as 1 nice picture, and upload the pic to Roll20 as your map -- there are some programs you might want to try. ProFantasy sells some great programs for this. Joe Sweeny has some instructional videos for making High Space maps using ProFantasy software. Look for his High Space series of 4 videos on here, <a href="https://www.youtube.com/user/joesweeney88/videos" rel="nofollow">https://www.youtube.com/user/joesweeney88/videos</a>