Open shelves with basket storage to left of fireplace would be nice.

Does that desk stay? what other furniture are you putting in this room? Need more photos to see the whole space, it's a mistake to design an isolated spot not knowing the greater context.

I see a large vertical work of art above the fireplace.

Ditto the modular desk/bookcase idea. If you're committed to building the window seat it should span the width of the window, be about 15" high and 20" - 22" deep. I do like the concept of a free standing bench or daybed a lot more. Relocate the art work, it's too small over the FP. Use a bigger piece of art above the FP and leave the wall to the left as it is. The impact of a larger piece of art will carry that wall including the corner.

Thanks! The pic we have now is just a fill in. Free standing bench is a good idea also.