Here's my post from an earlier thread. I'll try to post pics of the seats some time this weekend.
Both of my kids use booster seats. In my wife's 128i Convertible, we have two Recaro Vivo booster seats (
http://recaro.com/index.php?id=3330®ion=3&L=2). The seats are the perfect size, and we have no problems fitting the seats or buckling the kids when they're in the seats. So far, the seats are working out well, and my kids have no complaints about the seats.
I tried several different booster seats before sticking with the Recaros. The extended wings on the headrest work very well so that your child's head and body don't tilt over when they fall asleep--a fairly annoying problem I've had with other manufacturers' booster seats. The side impact protection adds to the peace of mind.
Prior to using the Recaros, I had taken an Evenflo booster--this was to be replaced by the Recaro regardless of whether it fit in the 128i vert because of its lousy design--and a Britax Marathon to the dealership. The car could not accomodate both of these in the back seats because of the width of the seats. With both Recaros in the back seat there is still room between the boosters.