When a spell requires you to see the target to make it work, it is said. Little illusion do not say like this:
You create a sound or image of an object within range that lasts for a duration.
It is only necessary that the target area is within reach.
However, there is one more general limitation that you must adhere to and that affects all spells: You must have a clear path to the goal (from the PHB section on Goals):
To be able to target something, you must have a clear path so that it is not behind the total cover.
And from the description of Total Cover:
A full-coverage target can not be attacked directly by an attack or attack
a spell, although some spells can accomplish such a goal by trapping it
in a sphere of influence. A goal has a total coverage when it is complete
obscured by an obstacle.
So, if the wall or door completely obscures the area you want to target with the spell, you will not be able to work little illusion,