Anyway, you are right about the contrast of between the first image and the motorbike the suit etc. The first image seems to give the idea of a teenager gang of some bad neighbourhood. But maybe they are just "bored semi-rich" kid kind of band, like kids from family with good wealth that play bad boys (we know about Aiden's Uncle). And/or the bike and the suits can be stolen or part of their little criminal activity anyway.
Also the two guys wearing the white and blue wifebeaters seems quite older than the rest, for sure not students and they are not in the 2nd image. Maybe they heard good things about Sophia and for the 3rd task they want to be there.
If only we had the infinite-zoom CSI technology, we could try to match one them to verify your hypothesis that the guys in the background in the teasers are from the gang...
