According to the search results, the latest Gang Beasts update is patch 1.21, which was released on October 4th, 2023, for all currently supported platforms. The update addresses a number of miscellaneous issues, but there is no information on any new stages or costumes that were added. However, it is worth noting that the search results include posts from different dates, and there may have been other updates released before or after patch 1.21 that added new content to the game.