Yeah finding a category that my pictures are mostly about will be a challenge. But to put it simply it would be fandoms generally. And technically that'd be a category. A various one but a category nonetheless.
Mostly family pictures, but that's only because most of the pictures on the computer are my mom's. My personal folders have mostly ディズニー characters and ニンジャゴー pictures. XD
Not being specific, a large portion of my pictures are of classic rock stars from the 60's & 70's. Being もっと見る specific, my Jimmy Page folder has the most pictures in it.
They are mainly pictures of アニメ and famous shows または actors, haha. For example; Supernatural, Jensen Ackles, Logan Lerman, One Direction, Louis Tomlinson, Ariana Grande, Fairy Tail, Zero no Tsukaima, My Little Monster and screenshots from tumblr, haha. That's a long list, sorry.