Back pack fetish.

So lately I've had this sudden urge to buy a backpack. I don't know why but i have this thing for the 1960's style backpacks.

I remember owning one of these sorts back in elementary school. I can't remember the brand name but I'm sure if i found it, I'd rock the sh*t out of it. Great way to save money.

I've also noticed a lot of these street wear brands are starting to dive into the 1960's style backpacks which I'm sure are gonna cost me an arm and leg.

My only question is, if i were to purchase one, what the heck would i keep in it?

For those of you who do rock backpacks, what do you keep in it? I'm here to take notes.