I made a backpack for the tree swap for hannahbear and my daughter immediately requested the same item except in green and purple! She even sent me the yarn! Here are the results:
I lined it with sections of a cotton towel I purchased at World Market. There are a couple of pockets, to accomodate cellphone, measuring tape, wallet, etc and plenty of space for a bottle of water or whatnot. I used a pattern from Patons http://www.patonsyarns.com/pattern.php?PID=2160.
The strapping was not adjustable in the pattern. I'm not sure what I did is any better, but here is a picture anyways -- I used D rings and velcro. As you can see, I altered the bag a bit in other ways as well-- I am always fooling about with something just because I can. Thanks for letting me show it off!