Scion invited the group over at Autoblog to its art gallery in Culver City, California last night, for a chance to preview part of the lineup it's bringing to SEMA this year. Parked out front was an xB that was transformed into a limo by Cartel Customs. The concept of a Scion xB limo sounds ridiculous, but in person it's ridiculously awesome. Rear suicide doors open to a comfortable environment outfitted with a…