I think you could work on the overall depth of your games. You know, add more gameplay elements, make it more than just one simple concept. And try to be original. Of course, don't forget to give the graphics more attention. They really need it!
To answer if you need to create more levels is up to you. Did people like the game so far? Do you like it so far? How much effort and time are you willing to invest in the game? And what is your personal goal for the game? Important things to ask yourself.
For now, I would recommend to improve your skills, and when you're ready, build and release a game that will have people telling you - "Hey! This is game is hella fun!"