A topic that has been requested before.
Post here all the ideas for tilesets you have always wanted, but could never find.
And if you really want to, tell people how much you want a certain theme NOT to be used again. =b

My ideas:

Beach ( I don't like the original JJ2 one. )
A sketch tileset, complete with new grey-and-white palette
Internet ( Yeah baby! )

And a well-made polar tileset would actually be nice.