There's always so much stuff to carry around, books, electrical gear, a spare band t shirt,your lunch! Music themed bags fulfill two functions, they carry your essentials and they make a statement about you. You can blatantly tell the world, "this is the music I like".
Looking for cool bags I came upon this shop on ebay at Eyesoremerch. They have tote bags or the ever more popular retro messenger bags. Bands available are, Asking Alexandria, Black Veil Brides, Cannibal Corpse, Rush, Bathory and Jimi Hendrix. Not strictly musical but the Robocop messenger bag is pretty good. These guys I found, also have a site at Eyesoremerch.com with a much larger range. All their merch is licensed and official so you know that the band is not getting ripped.
These Messenger bags are pretty versatile. I like the way that they can be worn over the shoulder or across the chest. They look pretty waterproof and have a secure velcro fastening system. The bags are made from polyester and feature inner pockets. Yep for school work or leisure use these bags are excellent.