I think the black grille is a no brainer, it looks really sweet on a black e9x.
Black reflectors are subtle and an easy/cheap mod that gives the front a clean look.
The black wheels are really the deciding factor. The apex arc-8 satin black wheels looks really nice. But again, might be too much black. And I imagine they are like a black car and look like crap when they are dirty.
Hyper black or gun metal might be a nice offset from all the black. The 2010 e90s don't have chrome trim on windows. It's all black.
2008 E92 Interlagos Blue Metallic M3
fully loaded with fox red leather and carbon fiber interior