Question: how to decorate a small living room without windows?
Answer: Mirrors. Adding a large mirror to your wall is one of the first ways to simulate the effect of a window, not just for bouncing some light but also for adding a sense of depth that breaks up claustrophobic wall planes. ... 
White walls. ... 
Large art. ... 
French doors. ... 
Hidden lights. ... 
Transoms. ... 
Internal windows. ... 
Frosted glass.