And what colour scheme?

yes to the built in! love it there. you could do built in benches w/storage,

cabinets, open, w/storage,

floating bench (which would leave you room for the dog bed)

or a settee option

ignore the round table. settee with a nice pendant light and warm wood chairs.

builtin. warm wood, and bring in some color w/cushions, drapes

Some great ideas thanks. Specially the one accommodating the dog bed. so overlapping the windows looks okay? it would be nice to have a back to lean on

Beth has great ideas and visuals, settee is the word I wanted. I see the warm wood you already have in both rooms, keep that element. It goes so well with any colors, especially blues and grays. I still think the windows will not allow for built-ins, maybe others will correct me if wrong.

Do you need the existing shades? Perhaps you could do some color in different window treatments. Lots of talented folks here to help with that.

since the windows are rather low, and they take up the entire back wall, it's going to be hard to find something that allows you to lean back. maybe have a 'lean back' portion on either side?

or, you'd have to do some large pillows for support

this is a low set window. you'd have to use pillows for back support

notice on the end how you get pull out storage

types of settees you could check (they sectional together too)

perhaps if you did something like this, it would be ok to cover the lower portion of the window?

Or if you just did the settee w/a back on one side, (only you would pick one w/such a high back)

or find some other types of benches instead of built ins

and the floating ones

You could definitely get away with a backless custom built-in bench. How tall are the bottom of your windows from the floor? Make sure you account for that when you add a custom cushion about 3" thick. Many people just like to use throw pillows as backs, which can be rearranged without obstructing the view outside. :)