Through a glass darkly

One window of the ongoing factory model is in the 'backdrop' wall so can't be 'open' like the others.  Rather than just leave it black behind the glazing I thought I'd see if I could give the impression of an inside.

A bit of a rummage for 'factory internal' images eventually turns up something with roughly the right perspective and lighting which I can tweak.  Probably no-one will notice, but I will.