I would get rid of the mirror and do a huge gallery wall! I like ur lay out, BTW, do you have a buffet table behind the sofa? Either push the sofa more forward or push it all the way against the wall.

Welcome home! Don't go black with the shelf area- it will look like a black hole. The trim color would look better, and just on the wood. OK, on to the window wall. Leave it open- the doorway from the kitchen is right there and you would be blocking both the view and the doorway with another piece of furniture there. Just figure out how many people you want to seat in the space, and choose your new furniture that way. The configuration you have now is working pretty well. Take some time to get settled in before you try to get the whole space done, or you might make choices you regret later.

Do you need more seating options? I like your big window and wouldn't want to block it somehow, but if I needed more seating, I would probably go for a nice wooden bench with cushions, something light which could also be easily moved when needed. Just an idea:

Ashby Bench, Light Wood · More Info

This is one of the few rooms that seems to be able to take a large sectional. Live with it a while as sooz001 states. I like your unique spaces. Although (and I don't believe I'm saying this) painting the cabinets and shelving off-white will make it look better. Edit the space too.