The subject begins in the Radvaz’s, commentary of Rabbi David Ben Zimra (a”h), who wrote am answer that discussed praying in front of a mirror where you are able to see yourself. This poses 2 problems.
The first is that when your eyes are open while praying the Amidah and you see your reflection – this can obviously take away from your Kavanah in the Amidah.
The second problem deals with closed eyes. When your eyes are closed, it appears as though you are bowing to yourself since your image is before you. Therefore, it is forbidden to pray in front of a mirror if your eyes are open or closed.
Ha’Rav Ben Tzion states that the halachot of praying in front of a mirror do not totally apply to a window. It is still a problem if you pray in front of a window with your eyes open as you come to see your reflection in the window. Seeing yourself would take away from your Kavanah. But if your eyes are closed affording you the complete ability to concentrate properly, then nobody would suspect that you are bowing to your own image, for you are in front of a window and not a mirror.
Therefore, according to this view – praying in front of a window is permissible as long as you close your eyes.
For that matter it would be forbidden according to the Halachah, to pray in front of a painting of a person or of an animal. Praying in front of an image of a person or animal might bring people to think that you are bowing to it.
Halacha L’ma’aseh is that when it comes to a mirror, it is forbidden in all cases. When it comes to a picture of a human being or an animal, it is forbidden in all cases. And when it comes to a window, a transparent window where there is a reflection of yourself, it is permissible only if you close your eyes.
