Everyone so far has said curly, but not all curls look great on a round face. Choose the one which beauty magazines call the "corkscrew" curls and have your hair layered first. I tried it months ago from the suggestion from my parlor and everyone I met said it looked good on me :)
Curly, straight, scrunched or if you go to here: http://funadvice.com/r/1599q9nuam1 it gives you 70 pictures of hairstyles with people who have round-ish faces. I hope this helps!
And for the length choose just below the chin if you decide to do a straight cut in layers. As for curly hair I find the length between the collar bone and the chest as the best
I'd have to say Kiera Knightley's short hairstyle would best suit a round face also nice good layers like in the picture I have.
medium length straight or curly looks great
A Bob!!! :]