I agree I don't want it to be overkill. I picked Winnie The Pooh based off the song Poohs Corner. Plus it's a gender neutral theme. I like the greens, yellows, an oranges too.
Lots of orange, yellows, and green.. try not to make too much with the characters so the room will not look too busy, just do the details like a lamp, the mobile, the stuffed animals in some strategic places (as one on the rocking chair, a few on shelves, maybe a pillow..) of course you don't have to do it like I'm saying.. but I think it would look very cute.