I think the game would really benefit from more movement options.

Walking-
The walk graphics already exist, as we can see when we are stunned. Why not create zones where moving slowly by walking is advantageous, such as around thorn hedges or fire? It can't be in most places because some players would always walk and the other players would get frustrated waiting.

Falling Down-
Monsters fall down due to our bombs. Why not let us fall down when we get hit by certain monsters or weapons, like when we get bumped by jellies or something? It would be fun and make the game a little more difficult.

Jumping-
Make a class of monster that attacks our feet, like snakes or something, and we'd have to jump to avoid damage. Or put more obstacles in the game, some that we have to jump over.

Swimming-
Ok, I know this is reaching, but we never get in water. Maybe make us get wet to slow us down like stun does. (Hard to move in all that wet armor) You could even make funny squishy sounds for us as we walk when we are wet or something.

Well, this is turning into suggestions, so I'll move it to there.