Thunderbrd
C2C War Dog
What you are sharing are simple 2d images. You cannot replace the 3d cities we have with 2d images.Perhaps it could just be a option or mod mod to add these city grahpics into civ4 C2C in the future eras.
Believe me, if we were doing a new game entirely, I'd probably prefer it to be in 2d art... much much more easily developed that way and would leave a lot more room in the mem and processing for more important things. IMO.