I'm just curious- are you using the fox engine, or one of your own?
Very nice tiles- I will critique them I like to think of tilesets as one of my fortes
Simply to make level dsign more simple, and to make the levels seem overall less busy, I would completely ditch the second "interior" tileset, and build it into the first. This way you can also build in an autotiler (scribble the level, and when the level creates itself, it cretes a tile depending on it's location, then if there are objects surrounding itself on four sides, it deletes itself, sorta thing- I'll send you an example if you like)
The grass, first of all, needs to be darker. It also needs to hang down over the edges, at the moment it looks like it's mowed.
http://img457.imageshack.us/img457/327/tilepng11ku2.pngSo that's a rough edit of what I mean. Edit- broken image, so I posted a link instead. Hope it works <_<
Also, study some of these, to improve your own
As a game
Download the game version of this tilesetyes, some showoff, but I really do think these will help you.
Awesome character and animations, btw!