Hang semi translucent fabric panels from the ceiling to tie in all the windows. It would look beautiful with your tall arched windows and suit the style you have going in the room.

A custom arched shutter stained the same color could give you a whole new look.

Panels do not have to be at the same heights. You can use a soft linen fabric to create a pair on the center window. Then on the side windows, create an asymmetrical look with a panel pulled back to the left and right of each window.

you could do panels, or inside mounted romans or cellulars, if you have the room.
on the arches, you can have them templated and covered with the roman/cells, or leave them open and start the shade down once the arch finishes, to allow the daylight through.

it looks like the arch shape is just an exterior detail though, so forget about templating the arches. your shades would be straight rectangles.

you could even get window frosting (it's peel and stick) and put it on the windows.
privacy + daylight! :D