Your furniture/colors sound wonderful! I do think cornices are dated looking. Others may disagree...

What about making a Roman Shade out of your beautiful fabric to hide the cellular when it's up? Either a real or a faux Roman? More current looking than a valance imo.

ETA: do you even need a cellular on a north facing window with no daytime privacy issues? No furniture fading. You could do a fabric roman shade and just lower it at night for heat retention if needed.

hmmmm interesting to think about. If I put a brand new cornice up today is that continuing a dated look, but if I have a cohesive room and it includes a cornice because the room was put together a few years ago does it scream dated when entering? IDK but what I know is I LOVE LOVE LOVE my wood cornices. DH made them and they will be in place until the day I leave this home. I am bolstered in my conviction by the compliments they continue to receive after all these years. Perhaps the shape/style/material in the cornice matters most?

Can’t help you because whether or not something is dated is irrelevant to me! I decorate for my own family’s function and aesthetics.

Arcy_gw do you have any pics of your cornices? Thinking of making one for our bathroom, since I have leftover material after making the shower curtain.

The Shade Store makes mostly contemporary window treatments and their fabric selection is contemporary and they fabricate cornices so I think they are not dated particularly if they are simple. And helpful for covering the mechanics of a blind.

Thanks to all who commented. I think a Roman Shade might be the option to cover the top of the blind. I don't want a roman shade to pull down at night as I am short and reaching over a window seat to reach 5'6" would be a strain. The cellular blind is easier to manage. I can't have cords because I have toddler grandchildren often.

Perhaps the shape/style/material in the cornice matters most?

From the ones I've seen lately, I think this is true. The simpler, less fussy shape/style seems to look more current. Especially with such a strong, vibrant fabric.

If you don't go with a simple cornice, perhaps a faux Roman, since you don't need to pull it down at night?

Is there a reason why you can't have curtain panels on this window. I have cellular blinds in the TV room and stationary toile panels on each side that are for decoration only. Would this work for you?

Panels don't work because there is only 3 inches between left side of window and the door to breezeway.