I've completed the History tab on http://tinyurl.com/GoWEvents that @Rasper had started.
Of course, it has no images, but it has links and it's searchable. I've added a few troops that were missed here, too, like Guardians, GW troops, Mongo, Ice Golem, and perhaps others. Anything before Steam official release (Nov-20-2014) was considered to be already in the game at the time of the release. There are probably a few errors or imprecisions, but the list should be close enough. It's really hard to find information on some of the older troops.
Thanks a lot for your Chronicle, @KAYA43V3R, it really helped me in the process!