You create the image of an object, a creature, or some other visible phenomenon that is no larger than a 15-foot cube. The image appears at a spot within range and lasts for the duration. The image is purely visual; it isn't accompanied by sound, smell, or other sensory effects.
You can use your action to cause the image to move to any spot within range. As the image changes location, you can alter its appearance so that its movements appear natural for the image. For example, if you create an image of a creature and move it, you can alter the image so that it appears to be walking.
Physical interaction with the image reveals it to be an illusion, because things can pass through it. A creature that uses its action to examine the image can determine that it is an illusion with a successful Intelligence (Investigation) check against your spell save DC. If a creature discerns the illusion for what it is, the creature can see through the image.
* - (a bit of fleece)
The Warlock invocation Misty Visions allows them to cast Silent Image at-will.
You can't since it is a concentration spell and you can only have one concentration spell running at a time.
Is it possible to use the “silent image” spell as pseudo-invisibility, creating a complex-shaped color blob around yourself, with some kind of texture, so that from the outside it loocks like empty place? Is it possible to move in such a cocoon and change it form if someone tries to touch it with their hand? Theoretically it should be possible, but it still looks like cheating, so i am not schure.
It's an interesting idea but I think it's really stretching the definition of "an object, a creature, or some other visible phenomenon". Check with your DM to see if they'll allow it.