^I'd like to create levels using that tileset, it's really well-made and very detailed, and very spooky, I must say. It would also go very well with the Zombie gimmick.
I would like to create custom tilesets; unfortunately, I do not have that artistic ability. Some tilesets I have in mind are:
Library: Bookshelves, books as terrain pieces, along with wood and staircases, desks, chairs and computers. There will also be a trap that involves a book falling down on a lemming. The library will be more modern than the one in the Castle tileset in Lemmini, which has a medieval look to it. (Come to think of it, I'm thinking of making some levels in Lemmini/Superlemmini using Lemmini-exclusive tilesets).
The style should be accessible to many since this one will use all smooth-edged terrain.
Farm: Grassy fields, fences and barns are the terrain, as well as gardens, vegetables. This is a mix of rough and smooth-edged terrain. However, the animals will not be terrain, because we wouldn't want our lemmings to cut them up, would we? Instead, they will simply be harmless animation, with some of them being traps (animals eating lemmings). There are two types of water: regular water, and milk.