A lot of graphics may eventually amount to a large sum of MB's worth of data, but it takes quite a few heads, shields and bodies to equal the size of a single mp3. However graphics are stream-line downloaded as needed, so you're not sitting there downloading many MB's worth of graphics at the same time. This wouldn't be the same with music which would have to be packaged with the app itself.

Very differently. Deadwood's lighting simply overlays a dark effect. However you can not subtract from the darkness, so you can't add more visibility around the player like I have in my screenshot. This CAN be done though with a fairly simple technique, but then you can't have more than one lightsource, which is what I was suggesting. There could be three routes for various quality, which I suggest let people choose to alleviate possible lag on various generations:

Simple: Like deadwood. It's dark, and light sources simply emit a light effect. This doesn't help visibility much though
Moderate: Draw a dark effect and remove the darkness around the player using a technique. No multiple lightsources possible, however give light sources in the level light effects
Advanced: Create a paneleffect that subtracts darkness from each light source. A more intensive method, but actually increases visibility around the player.