One of my players wants to create illusions of multiple creatures, for example, a band of orcs or illusory copies of the entire party fleeing the scene. Major Image would do the trick because the area is big enough for that, but per RAW it can't once it states you can create the image of an object, a creature, etc. The problem is there is no other spell that allows the creation of multiple illusions...

I wonder about that. Programmed illusion uses the same '"a person"/"an object" wording, but there is an official instance of it making a ceiling collapse (which has to involve multiple pieces). It is up to DM, but I think it can make multiple creatures as a single illusion.

Well, I understand that a collapsing ceilling is one whole object moving in a particular way, like, let's say, the illusion of a creature bursting into pieces. A dozen creatures performing independent movements is something else. Maybe the RAI is that one can't control that many illusions with the same action...