Ok First Effort
I understand the appeal of just using tweens a lot. But there are some things a good pre-drawn few frames of animation are best at. This piece of work would be so much more enjoyable to watch if you worked on the fluidity of the actors.
It's definatly worth adding some audio if you can, will definatly help the flash feel more alive, as right now it feels stale and unemotional. Thats what tweens do though, they're motion is too perfectly symmetrical.
As for the actual characters themselves, they looked great. You are obviously a natural artist. THe only thing you got between you and submitting great flashes is just putting that extra bit of attention into the animation.
I hope this helped.