What I'm trying to get at is not really what species of plant or anything, more trying to figure out if there would be a physical way of these leaves being on the mirror naturally, ie, if the wardrobes were outside or near a window or if the leaves were of inside plants or even plants at all or if they were, I dunno, drawings, shadows, etc.
My thoughts are, without really knowing the situation, that, A: sometimes a certain spirit will leave little mementos like that to say, "I'm ok, I'm around." Lots of times these come in the forms of random feathers or flowers popping up where none were planted. But leaves, I believe could be used as well. Or, B: whatever spirit that's around is trying to cover the reflection for some reason? Some people do believe that mirrors can be or create portals; some also believe that a mirror facing out a window will deflect spirits and prevent them from entering the house. Just my thoughts.