Get some black electrical tape or masking tape and line the underside of your airbox. It should give you an idea. I doubt it'll be a mirror finish because I don't think the red plastic is reflective enough but it could look cool. I assume it would just look like it does with the intact airbox since that's black.
If you want something flashy I'd get some chrome spray paint and paint your inner airbox, or even just use that on the inside of the airbox cover.