They are so little--I would not cover them at all. Black out is really not a necessary thing.

These are some tricky windows. Does the 1/4 arch window have a screen with a hinge? If you don't need the screen you could do a shutter or honeycomb shade that follows the shape of the arch. If you're into DIY you could also make a template of the window and cut a piece of wood to follow the shape of the window and wrap it with fabric and hold it in with a magnet.

For the other window a shutter or simple shade would work.