A sewer! Oh, wait, you did Prison Sewer... A BETTER sewer!
Or... a tropical island, perhaps.
Maybe a mountain?
Oh, make a castle tileset! I know there are lots of them, but none of them has any outside stuff in them. Don't just make the castle, make the forests and grassy plains surrounding it. Oh, wait, that's gonna make a big tileset, not a small one...
Bah. Can't think of anything else.

I claim page 2!!