- Since the visual part is the key component of your game, I would posh the quality of the shadows a bit more. Now, when you start the game the player gets a view with quite some visual artifacts. Using trees with thin branches and a few leaves don't make that easy, I know :)
- Add anti aliasing.
- There's only one quality setting, I would add a few more (certainly for those people that want anti aliasing.
- Polish your startup experience, check Gravity Rush (another entry to this jam), he/she did that very well.
- Foot step noises
- Feedback on picking up a sphere is a simple text counter "1/14" flashing briefly on the screen, you could improve that experience, with a feel that fits the mood of the game - with sound.
- Music
Are a few things you could do off the top of my head.