Stun, Daze and similar stuff don't impede your movement...
...they make your mind funny.
While you are stunned, there's nothing holding your body to move. You just can't think right to actually do something. If you take a really hard blow to your head, that won't make your body harder to move - it will make your brain go gonzo for a few secs, before you became aware of what's really happening.
Stun is not about movement, is about senses of what's going on.
Freedom of Movement makes "your body work right", not anything else. It allows you to move, but not allows you to think. You can't think if you're dead. Or Stunned.
Paralysis don't block purely mental actions, so it don't block "thinking".
Slow makes your body... well, slower, but it doesn't affect your thinking.
Web is... well, a web. It hinders your body, not your mind.
Stun, Daze, Dazzle and similar stuff, on the other hand, makes your senses go wacko, so they aren't really blocking your movement. Stun never stopped you from moving, it just stopped you from thinking for a while - and since you don't think, you don't act.
So, the point is,
If something affect your senses, Freedom of Movement can't help you.
Think like a "Houdini Effect". Houdini can escape from almost anything, considering that he
knows what's going on. If you throw him with a concussion inside a closed coffin... well... he will stay there.
So, to determine what Freedom of Movement removes or not, use a simple rule:
Why I can't move?
If you can't move because a spell or something is hindering your body to move, like Web, Freedom of Movement can help you.
If you can't move because a spell or something is making your brain go gonzo, like Stun, or because your body becomes something that can't normally move, like stone from Flesh to Stone*, it won't help you.
*Flesh to Stone don't impede your movement, it merely limits you to the movement that a stone statue is allowed to do. A "Freedom of Movement"-ed and "Web"-ed person would become a completely untangled stone statue.
Also, read Freedom, the 9th level spell:
The subject is freed from spells and effects that restrict its movement, including binding, entangle, grappling, imprisonment, maze, paralysis, petrification, pinning, sleep, slow, stunning, temporal stasis, and web. To free a creature from imprisonment or maze, you must know its name and background, and you must cast this spell at the spot where it was entombed or banished into the maze.
Emphasis mine.
Freedom removes a bunch of effects, like Flesh to Stone and Stun. It would seem rather... strange to say that a way lower-level spell can do almost all the things that a 9th level spell can. Freedom is Freedom, not Freedom of Movement.
There is no restriction that the illusion cannot occupy the same space as a creature (it is not a creature itself and the text does not mention it). You can also create the image of a creature you can see easily and slight modifications, like the lack of wounds should be within the capabilities of the spell. The only hiccup could be with moving the illusion to overlap with the creature at all times. The spell does not state that the image can move by itself, only says that:
.. you can use your action to cause the image to move to any other spot within range. As the image changes location, you can alter its appearance so that
its movements appear natural for the image. (PHB 258)
The precise details will be up to the DM, but it seems reasonable to rule that if you spend your action every turn on moving the illusion, it can stay overlapped with the creature.
Limitations
Unless you are a high enough level wizard of the school of illusion, you cannot change the image after you have cast it. You cannot make only some wounds appear.
You can only cover things up, you cannot make anything disappear. Like possible sprays of blood from a really damaging slashing attack.
About the image giving orders
Unless the real creature is mute and/or deaf, he will also hear the things you make "him" say. It might give away your trickery sooner. Also, he can just override your "orders" with his own. You might create some confusion in the ranks, but then some of them will surely make investigation checks to clear it up.
Best Answer
The various "image" spells are basically a carte blanke to do anything you can dream up, within the stated limiters of the spell. You manipulate the spell with your concentration, and can alter it as you please as long as you do not take the image out of the limiting area of effect or attempt to do more with it that then the spell allows you to do (i.e. produce any sound or thermals with Silent Image, or recognizable speech with Minor Image).
Illusions such as these are staples of fantasy fiction; why would you assume you can't create a fluid effect with these spells?
For example: an illusionist, hidden in a room whose volume is not larger than his AoE for the spell, casts Major Image: that of an egg in a pentacle. When the door to the room opens and creatures enter, the mage has the egg crack open and a mist start pouring out. in a few seconds, a vicious horned demon forms from the mist. If the creatures do not attack it, the mage then holds a conversation with them out of the demon's mouth. If the creatures attack it, he disperses it into mist again, mocking the hapless creatures.
As long as the mage concentrates, all this is within the purvey of the spell.