buy some art. we can not see any of your taste in these photos. please post pictures with room content.

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Either hang some great, substantial photos or artwork. Add some cohesiveness by framing them all the same color. Good luck.

A colored piece of art will brighten up your wall.

You haven't shown enough of the room or furnishings to make complete suggestions. We need to see all four walls from at least two ends of the room so we can see where your doors, windows, and light are coming from. Here's a guess based on what you do show:

What about a very long wall unit with bookshelves and a place to put your TV, assuming you plan to have one in your living room? Then on the wall to the right perpendicular to that a large piece of art? Think about getting a large colorful area rug in front of your couch/chairs to anchor a space for a coffee table. (Do you have a couch?)

Color schemes to accent the black and tan--turquoise, lime, yellow, bright blue.