The best alternatives to Dungeon Alchemist are Terrain Tinker, RPG Maker MV, and Cräft!. If these 3 options don't work for you, we've listed a few more alternatives below.
Terrain Tinker is an online tool that allows you to design buildings and dungeons for tabletop games to 3D print at home. We use the great 3D printable models from Printable Scenery. Our Kickstarter has less than a week to go!