Pottery Barn Roman Shades. Love the idea of 2 shades on the big window (instead of trying to find huge blinds/shades for whole length!).

Mueble contra ventana - Ropero o Cajones Kids' Curtains, Kids' Area Rugs Kids' Room Rugs

Contrast bordered Roman blind given that added interest with a pelmet were we have turned the stripe & used the fabric 'rail-road'

Contrast bordered Roman blind with a contrasted stripe pelmet where the fabric has been 'rail-road'

Cutout cornice around moulding

This could work as a shelf above the octagon window, hiding a light-blocking fabric roll-up shade.