Just finished making all LODs levels (L0-L4). Some people don't care about them, but It's necessary for proper game optimization, even on Hi-end PC.
L0 (playable model) ~99k polygons
L1 ~ 70k
L2 ~ 25k
L3 - 7653
L4 - 416 polygons
And for example how it looks ingame:
L0
L1
L2
L3-L4 spawns on very long distance, so you won't notice any difference.
Also make interior paintable with 2 different colors and add some extras: