Have you considered drapery panels? They can be lined with blackout fabric and be used to add texture and pattern in the room. I found really good quality pre-made panels (I know that sounds like an oxymoron) at Fabriclalnd with blackout insulating.

You have lots of options with a triple window. You can mount roller shades for black out purposes by mounting them to the top of the window frame on the inside as you probably don't have sides on the middle window.

You can do roman shades the same way and get a single valance across all 3 to make it look more united.

You can do woven wood blinds the same way.

You can also do bottoms up/top down shades like duettes.

If you instead choose to mount outside the window frame, you can do drapes on rings or better on a traverse rod that will close and open easily.

You could also get vertical gliding blinds or drapes...check out what hunter douglas has to offer. These are more modern and neater than vertical blinds.

You could also do a combo, for example woven wood blinds with drapery panels in between to hide the breaks in the blinds, but that will cover more of the window.

{{!gwi}}

...and yes, you can get woven woods and romans lined with black out material.