This could either be rudimentary external software or built into the game, but Party Animals would thrive with an map editor. Steam workshop could be a good consideration for implementation. Community creation keeps the game alive and brings people in. Granted a lot of current map selection are built around interactive aspects, but even just simple textures/assets, Item spawn locations, player spawn locations and you have yourself deep replay value.
Going further as a side addition for Steam Workshop would be letting the community make assets, maps, to EVEN skins? This allows the Devs to be able to hand pick creations and add them to the game in the default selection.
Overall if you give your community tools, they will assist the content additions.