Cute house, I love older character homes, IA with veliska27 with a little TLC it would be great, although it is already charming as it is.

I see what you are noting however I think it is just combo of reflections, artifacts distorting the reflection, and perhaps even something in the window [bit of a curtain showing under the blind just for e.g.].
The photo is quite pixilated with notable artifacts [likely due to aggressive compression], the foliage looks stretched in spots, the roof, eaves, stairs, etc all have distorted bits, can also see artifacting in the other windows.
I'm guessing if you had a full res [unaltered] copy of the photo you'd find that the anomaly in the window looks different then it does here.
When images are downsized [image] details are removed [tossed away as you can't get original details back once you've saved the change], not uncommon to see upwards to 95% [or more] of the details [pixels] removed with images posted on the web.
This can make a huge difference, to how the overall image looks, whether or not you can discern details in the b/g area or smaller content objects, and the amount you can zoom in before distortion/artifacts/blur/fuzziness become a problem.
Just for example, on another forum someone posted an image where an object in the b/g area was in question, it was noted as being a small chair [child size] that appeared to have what sort of looked like a childlike figure in it or in front of it [also had a mundane orb over it which added to the illusion]. A request for a higher res copy was made and once posted it was like night and day, the chair was actually a couple of wicker baskets [stacked] sitting on the floor and the sort of figure [created by artifacts] was no longer evident.
With all that said, w/o an original full res copy you can't be certain what it may or may not be, however, IMO based on how it does look [& above noted] I think it's something mundane. Even if there wasn't anything in the photo I'd still enquire about the history of the home if you are thinking of buying it. Good luck with your search for a house.