This game has a ton of potential, I think. The gameplay is simple, yet still kept my attention for a good while. My suggestion for an easy way to increase the visual appeal without a ton more work would be to randomize the coloration of the other leaves a bit. Most game engines have a way to modulate the color of a sprite a bit without drawing a new one.
Long term, adding a few swaying and twirling animations to the main leaf, you could narrate a story, or poetry behind the gameplay and have a REALLY captivating game with that alone.