I'm loving these sprites!!

Umm, minor question, doesn't Dorothy have red ruby slippers? Or is it different in the books?

I'd add more vertical rotation to the lions face, like his snout getting higher and almost level with his eyes or somethnig. Right now it's very straight on. I'd also add some detail to the tin man's arms. His legs have black points where his joints are, so maybe his arms could follow suit?

Also, where's Toto? (lol)

Ok, I'd say it's just about done...

I agree with Larwick that the little monsters are both cute and awesome! But the right hands on some of them seem to be too far to the right. Judging from the angle it looks like they'd be more to the left.

It looks like the balloons are dithered, but the clown isn't?

Most of your problems seem to come from basic anatomy issues. The sign could be more realistic too, check out this tut: http://pixel-zone.rpgdx.net/shtml/tutmini-wood.shtml

The hands are parallel with the camera, and so they look really flat. There's no real volume to the pants, the clown needs realistic shading, the position of his feet are off, the suspenders should contour to his body, his hair should be more random and less symmetrical, and the balloon strings need to be less randomly splayed and more realistically relax, ala gravity. Also use less basic/primary colors and mix it up with some desaturation.

Your biggest problem seems to be that you have strongly colored outlines around the blades of grass instead of letting them blend more. Plus they're all pretty flat and expanding from central points. Note how the blades of grass in SD3 are curved and blend together. And very few of them have highlights.