Curtain of Guise

Across a space of 10ft square, you magically draw a screen that shows an image of your choosing on one side. This illusion is a stereogram that can allow a three dimensional image to be viewed from any angle, so long as it's from the showing side. This image can be an overlay of illusions over what is really there, a completely fabricated scene, a reversed image of what's there, a mirror image of what's in front of it, or even a hole or cavity where there is none. The illusion can also be designed to hide what is there by removing it from the scene, or by adding things based on description such as "Make everyone appear to be wearing different masks", or "Make the animals appear huge". Using your description of it, you can decide how the illusion accommodates for creatures and objects that enter the illusory area from any direction. The illusion can show motion but no sound at 2nd level. 

When viewed from the other side, the curtain appears nearly invisible. Any creature taking an action to make a successful Intelligence (Investigation) check versus your spell DC from either side can determine the presence of the curtain, the illusion becoming a faded image when viewed from the showing side, or a faint glimmer of colours and lines from the hidden side to that creature.

The illusion can only be designed to change the appearance of up to 10 feet behind it. For example, you could fill a hallway with writhing flames but only the first 10 feet of the hallway. If you make a hole appear in a wall, it can only appear to be 10 feet deep, with the rear wall being the image of a surface that you choose, or showing the real wall by default (as if it had been pushed into the space). 

When a creature that is unaware of the illusion moves through the curtain from the showing side, the illusion continues to cling to their eyes, and they must make a Wisdom Saving Throw. On fail, they continue to believe the illusion, seeing it as the way the illusory curtain showed it. Once per turn if they come into contact with a creature or object that is hidden by the illusion, or something that is in the illusion but not really there, they can make another Wisdom Saving Throw to see the truth. Otherwise their mind will rationalise the contact (for example, believing they didn't actually touch the thing they saw, or that some magic is keeping them afloat if they walked onto an illusory hole). Creatures that have this illusion appear as a hole on the ground below them are knocked prone if they fail their Saving Throw.

Creatures with with both normal and blindsight might have advantage on their Intelligence (Investigation) and Wisdom Saving Throws, depending on the nature of the stereogram. Creatures with True Sight can see both the illusion and reality.

At Higher Levels. When cast using a spell slot of 3rd level or higher, for each level of the slot above 2nd level, you can increase the size of the curtain by 5ft on each side, and it can depict an area 5ft deeper. The curtain can also produce sound to accompany the images, enough to be heard from a distance equal to the depth of image. The curtain can also provide a sound screen that absorbs all sound that would leave the depicted area. Finally, the duration of this spell changes based on the slot used: Concentration, 10 minutes at 3rd level; Concentration, 1 hour at 4th level; 8 hours at 5th level (no concentration required); 24 hours at 6th level; 1 week at 7th level; Permanent until dispelled at 8th level; Instantaneous (Permanent and can't be dispelled) at 9th level.