ERGONOMICS AND USABILITY-----------------------------------------------------------
An ADJUSTABLE strap is a must. I'm 6 ft 3 in heaight, and most straps out there aren't long enough for the bag to sit comfortably behind my bum.
You'd need the bags to be big enough to house a 15" Laptop, and a few folders or books, as the average person who needs a bag in the first place needs space for their things, usually at school, college or work.
Also,
you'll need roughly 3 extra pockets or hidden pockets, as girls will also be using these bags, and need spaces to put make up, and anybody needs a space to put their phone or MP3.
AESTHETICS------------------------------------------------------------------------
Consider doing
limited edition bags, such as A DUREM bag, a GAMBINO bag, an AEKEA bag, etc.
I would personally love an
OMG bag, or at least Mini Devil and Angel wings themed bags.