The game itself is alright for a practice game. I like the way you used textures, masking I'm guessing?
A few recommendations in-case you're wanting to go deeper into flash:
Have tut-tips! example would be at the beginning here tell the player to use arrow keys.
Start using pre-loaders, especially when the file size is this big.
^ don't make the file size this big :) use compression to scale down the music size.
Get a decent sound library for sound effects, it drastically enhances the game.
Reduce time it takes to get to gameplay. (Average flash game play session is 4:28)
Keep the gameplay responsive, such as unrestrictive movement like jump+move viable.
Implement scoring systems and high-score tables to allow competitive gameplay.
Always have a non-biased tester before release.
Anyways, good job programming the engine, it's quite nice. Keep working at it and you'll have a great game in no time ^_^
Best of luck to you,
~Jo