Sure. There's a lot that can be added to a game like this, I think, to enhance the experience.
1. As of right now a single battle doesn't last very long (or maybe just that I am not very good, hehe). So I get killed maybe after 5 minutes or so. So perhaps more pickups would be nice, or perhaps to have different types of pickups. The only one I came across so far restores a bit of your health, but what if there were more - like a pickup that increases your attack power for a few seconds or defence for a few seconds or makes you move faster for a few seconds, etc.
2. More different arena locations definitely. I would love to try different areas, especially if they differ from each other. As I mentioned in my first post, I think some environmental kills which the player could use against the enemies would be nice.
3. More enemy variety is also always a plus.
4. Possibly more weapons or special moves could be nice too.