When my guys were teens, they were very much into sports, so anything related to either the sport they participate in, their favorite sports teams, or the college they plan to attend would work well.
If they have other interests, like cars or motorcycles, then something related to that interest would be good.
I was not yet quilting when my guys were teens/college age, but I did do counted cross stitch pictures for three of them...an eagle over a mountain lake, a castle with a dragon, a tiger with cub...did not find ones I/they liked for the other two.
And of course you can always ask them what their favorite colors are and just do a quilt in those colors.