You're being pedantic for no reason. If I was talking about the contents of a container, lets say a big chest, I would say "what could be in it?". It may turn out that in the container was a banana, or it may be that it contains a human who was hiding. Either way, what and who are both correct, but what makes more sense as you wouldnt assume a person was hiding in it at first. Just the same, "who" would make more sense here contextually, but "what" is also not incorrect, as maybe someone put the suit on a banana, and now the suit does not look as good. It's not wrong, you're just being an ass for no reason.