Ever since the flag update (I think) it's been impossible to place a mouse spawn, you can add a hole which can double as a mouse spawn, but only having the hole as the mouse spawn removes so much creativity.

If you go to the map editor under Mice Items, and click Mouse Spawn, it will show Hole and Mouse Spawn both selected, except only hole will spawn.

This also appears to be the same with Shaman Spawns, only Cheese/Hole's can be added to the map :(

edit: OMG BUT WAS SUPPOSED TO BE BUG LOL WHAT

Shamousey said in a thread like this about the same thing that Pikashu said it should be fixed now o;