If you pull up the wheel diagrams (using one of the online part database sites like realoem.com/bmwfans.info/bimmercat.com) for any of the f06/f12/f13 wheels...you can find all of the BMW 18" wheels that were offered and I believe the smallest you can go in order to fit over the brakes is an 18" wheel.
You can then use google (or any search engine of your choice) and type "
BMW (type bmw wheel style # here)"...this should give you images of BMW 5 & 6 series with those wheels mounted (the f10/f111 & f06/f12/f13 share many of the same wheels...and the recommended tire sizes are the same, too)
I run 18" style 37 MPars (from my old 1997 e38 740iL) with dedicated winter tires. They are for function...not form (or beauty)...but you can see what "fat" 18" tires look like on an f06. Please excuse the dirty car...these pics were taken right after the wheels/tires were mounted...in fact you can see my 20" wheels/tires bagged up if you look through the rear windows:
Wheels:- front - 8"x18" w/13mm offset
- rear - 9.5"x18" w/25mm offset
Tires:- front - 245/45/18
- rear - 255/45/18