The most clever use of this I've heard is producing a fog, which creates visual disadvantage against physical attacks...

...and creating an illusory flame to make it appear as though you are on fire. For distractions.

Step one. Make a box.

Step two you put your rogue  in that box.

 Now you have your rogue in a box! 

Casting Spellword is:

Duplitucus Wonderium

My warlock can cast this spell at-will with Misty Visions. My favourite use is to send my imp familiar (from pact of the chain) into the dungeon ahead of us to scout. Then create the illusion of a map that is updated with the imp's knowledge as we go. This lets us track enemies and which rooms we've been to. It has been incredibly effective.
Basically I combine 2 features to create a Marauder's Map kind of thing.

A bit weird that you need to not be silenced in order to use Silent Image... even though images are generally silent already, so I'm not entirely sure why it's called Silent Image

Any thoughts as a Warlock who can cast this "At Will without expending a spell slot", in making multiple illusions over the 10 minute period?

It would still be casting a new spell that requires concentration, which RAW, sounds like a no to me. 

One of my favorites is producing a fake Globe of Darkness. I call it Faux of Darkness.  Especially bolstered by Dark Elf Characters. It works great for Rogues. It seems extremely difficult to realize its an illusion. The only way I thought of, is perhaps not being real darkness, actual shadows are still made outside of it from light sources around it. That’s an incredibly obscure aspect, but at least it gives some RP in game reason to be able to roll investigation versus it. That’s assuming a lot of subtle and obscure variables and with its sheer surface area many character shadows might fall inside of its radius. Perhaps only large ones stretching beyond it. Anyways it would be a pretty obscure thing to be able to notice in the heat of combat, but still possible for game purposes. In effect it is another really nice way to make solid illusion cover. 

Yes, I believe each one ends when the new one begins. Whenever the new focus of concentration begins. 

Physical interaction with the image reveals it to be an illusion, because things can pass through it.

 

What happens when the illusion is of fog, and things are supposed to pass through it?

Ranged attacks should pass through it without any indication, but a mostly naked person might notice a lack of humidity standing inside of it.

The writers here have no imagination.  It's always an animal to demonstrate movement or a wall to demonstrate that touch gives it away, but never something like smoke, fog, darkness or anything that you can't touch...

smoke and fog react to movement through them via air currents, if you swished your hand through the fog or fired an arrow through it you could see that fog/mist/smoke etc was static and didn't react to the movement. Silent image also can't create light as that falls under "other sensory effects" (see minor illusion). Darkness i believe would also not work as it would also be a "sensory effect" but in general since the creation of darkness is a second level spell effect, i'd say it is outside the realm of this spell either way

Step 1: Have access to this spell as a Thief-archetype rogue

Step 2: Cast the spell on the area you plan to steal things from

Step 3: As you steal stuff, update the spell with illusory versions of the items you stole

"other visible phenomenon" is nicely vague.

If you had a familair scouting an area. Could you use silent image to show your party the area ? 
Which you could alternate Turns' Actions back and forth the familar and the Image to 'update' with a slight lag

or if you read someone's memory c ould you pull a holodeck 'showing'?  etc

Would be intersting to combine familiar vision+silent image+that sound making cantrip to recreate a conversation

Would anything stop a player from using this like a poor man's Mirror Image with just one illusory copy of oneself? (Another limitation would be that you'd need to control its movement with an action, so the real player and the image would not necessarily be as indiscernible as with Mirror Image).

Quote from Mecrutio >>

smoke and fog react to movement through them via air currents, if you swished your hand through the fog or fired an arrow through it you could see that fog/mist/smoke etc was static and didn't react to the movement. Silent image also can't create light as that falls under "other sensory effects" (see minor illusion). Darkness i believe would also not work as it would also be a "sensory effect" but in general since the creation of darkness is a second level spell effect, i'd say it is outside the realm of this spell either way

 Smoke/Fog - I agree that they move in a certain way, but still - interaction with those types of effects should not *instantly* give it away, but rather allow for a intelligence/investigation check to discern it's an illusion, albeit with a lower DC than just plain looking at it. That'd by my DM call, anyway.

"Other Sensory Effect" - While creating light itself might be tricky indeed, creating darkness couldn't be simpler: Just create a large blob of pitch black colour - it's still very well within the limits of the spell, as you're creating literally just an illusion of an "object" that happens to be a 15x15 cube filled solid fully with pure blackness. Even light spells such as Daylight wouldn't counter that, but - of course - Dispel Magic would.

the an object a creature part of the spell, is that a numerical limit of 1.  Like you can only create one orc, one box? If the boxes are connected is it more than one object or just one. If I create a wall I'm hiding behind and connected to a part of that image is an illusion of myself near the top climbing onto a nearby roof to seemingly escape is that 1 thing or 2?

how does this affect in combat?   if a wizzard just produce a copy of himself,   to run the other way,  doest the blackbear need to run after him and  attack it to  know that is a fake ? does it need to expend an action to do so, and if it fails ? 

I dunno, I feel like light certainly qualifies as "other visible phenomena" and the "sensory effect" it is effecting is visual.

A Bard who multiclasses Warlock for two levels can unlock the “Misty Visions” Eldritch Invocation...gaining access to unlimited “Silent Images”.

This, in theory, allows them to become the ultimate storyteller...crafting imagery to go along with their stories.

It’s a fast way for them to become the most popular person in the tavern.  : )

It has verbal components as a part of the spell requirements. Indicating that you have to be able to speak, as well as sign part of the spell to cast it. Which you cannot do if silenced.