Just a suggestion! It would be cool if you were able to add music to your game (could be looped in the bg or based upon different rooms you enter, customisable by dev). No problem if it's too tricky or in the far flung future, though!
I feel like being able to upload your own audio is a bit too open. Bitsy is great because of it's limitations, and if SFX / music features were added I feel like they should reflect that ethos. A small sequencer, one channel, 2 octaves, 3 or 4 preset "instruments", would be enough for music. 5 or so pre-made sound effects that cover some basic actions like something being opened would cover the SFX front.