The air does not provide a surface for projecting an image. The ceiling might do.

Changing display fonts could be doable, and even another valua added sale for the providers, but you have to have the right font to display decently on a phone display, and have enough memory for it ( although flash is getting cheap)

For a projector call display, doable, as come alarm clocks do it.

Nice idea.Instead of showing by light, the phone would call the name appeared in the screen, if it's new number, just ringing.

Sand, I have to disagree with you this time. See regarding "Free-Space Displays"

But I think the power required might still be too much for a cell phone to produce in the space allowed. But the cell phone can talk to you with whatever you want to know. My phone tells me who is calling and what number they are calling from.