Get a patterned tile and stick it on, or contact with a pattern or just a pretty piece of card.

try white paint directly on the glass to conceal the roof see how it looks before you attempt something more expensive although one two or three pieces of white painted timber glued into each separate window would echo the line of the horizontal rails around the stairwell

yeah gee that's a tough one! I think I'd go for one of those peel and stick kinda solutions...what if you also painted out little black squares up top of the window...for symmetry?

Brown paint and green paint . Paint a wavy line 50cm up each pane , 4cm wide tapering as it goes up . Paint several branches off each trunk , also in brown .

When it's dry , paint green leaves on each branch .

The black is the pots that hold the shrubs .

My sister added paint to her windows in her art studio like that to disguise cracks. Buy some relief paint pens. They are great to create thin raised lines. Can get on eBay in diff colours

I would use painted white timber the same size as the frames individually set into and across the top of the black squares and then paint that glass white or another colour, a bit like leadlight panels