I don't know if this has been linked in other parts of this forum, but this needs to be here. I'm absolutely amazed by the amount of information and detail in this. Just wow. NOTE: THIS IS NOT MY WORK! Click through for larger. There's a Download button on the right for a gigantic size, and a link in the description for the key.
If you click through to the artist's main dA page there's a key to who they all are, and a discussion of why he picked them as well...
There is a link to a key on the artist's Deviantart page, for those who want to check their answers after...