The question surrounding the permissibility of davening facing a window where one can see his own reflection, arises from a discussion of the Radvaz (a”h) regarding the idea of davenung in front of a mirror. It is forbidden to pray in front of a mirror for two reasons. First, the sight of your reflection may likely disrupt your concentration which should be focused on your tefilah. Secondly, when you daven in front of your reflection, you give the appearance of bowing to yourself.
Ha’Rav Ben Tzion Abba Shaul (a”h) ruled that one can pray in front of a window if one keeps his eyes closed. Closing one’s eyes avoids the problem of the distraction caused by viewing oneself. As for the concern that one may appear as bowing to himself, he states that this concern does not arise when one prays in front of a window. Even though his reflection is visible, he does not give the appearance of praying to himself, since the window is not made for the purpose of providing a reflection. Needless to say, the simpler solution, when possible, would be to move to the side so as not to stand directly in front of the window while praying.
In addition, just as one may not pray in front of a mirror even with his eyes closed – it is similarly forbidden to pray in front of a picture of a person or animal, as this would give the appearance of bowing and praying to the image.