I think

that there's a few possible natural explanations. What do you see? Often, windows, particularly ones that are coated with something, when slightly flexed, will show a pattern like this. It's the way the light bends.

Faithful See Virgin In Hospital Window

"Hundreds Drawn To See Image, Pray"

I, too, commend them for their faith, but I think that this is like a viral video. One person sees it, and sees something in it, and tells someone else, and so on...