The original BioShock was created using Epic's Unreal Engine
3 2.5. Let's imagine, though, just for a second, that it had instead been built using Crytek's fancy new CryEngine 3.
The same tech that powers Crysis 2, it would certainly have allowed for larger, more expansive depictions of Rapture than the 2007 original allowed.
These screenshots, mocked up as a part-time thing on the side, were done by Scott Homer, an artist working at Crytek's UK satellite (the studio formerly known as Free Radical). He calls it a "homage" to the game, and it's a good looking homage at that.