Hi Wraithward and welcome to the guild. You may have a look to rpg map editor (https://rpginferno.com/rpg-map-editor), very similar to ANAMap with some more tiles but I am afraid it has the same map size restriction. If you discarted Dungeon Painter Studio because it is not free, you may also try Dungeon Painter Online (http://pyromancers.com/dungeon-painter-online/), the "ancestor" of DPS. Not exactly the same product, discontinued, less tiles (not the same tiles rather) the UI is a bit similar to DPS. It is free, online, with a larger map size than ANAMap, much much more assets and you can use your own tiles.
Regards