Interesting - I do not see your images in your post (replaced with ads) but they show when I reply to you. Sorry, I cannot address your question.
So the two imperial ones are the Gamma and the Alpha. The Alpha was only available to Kickstarter backers. I'm not sure anymore what the story with the Gamma is. And I don't recognize the other two. Were those pictures taken from some concept art? It seems vaguely familiar.
The first two are both from the commander concept page for the tank commander- neither were actually produced so no one has them.
They absolutely exist as modeled and rigged commanders, as has been established before. They aren’t in the game for some reason though.
They're not in the files; they were featured in one of the livestreams when Uber was showing how they tested anims on different model styles for each rig to make sure the way they animated would work for a lot of different commander styles.
You can find all the commander images in "<PA Install Directory>/media/ui/main/shared/img/commanders", where <PA Install Directory> is the directory you installed PA. That location can be found here: https://wiki.palobby.com/wiki/Planetary_Annihilation_Installation_Directory