The Toy Box is one of those features eagerly anticipated by those of us with serious inventory problems. There are oodles items that aren't useful, but we'd like to keep for the fun factor. The Toy Box UI has been implemented in the Warlords of Draenor alpha, accessible through a new, third tab on the pets and mounts UI. Unfortunately, I'm playing through the alpha on a template character -- an automatically generated level 90 with no toys whatever, as you can see in the screenshot above. Alliance characters, where most of my toys rest, are disabled entirely for the current phase of testing.
A larger screenshot of the full UI can be found below the cut along with a list of all items currently categorized as toys.