You have a sort of denim blue tone, so my first advice is to add some print that has shades of brown (wood, blinds, leather), denim blue tones (pale to mid-tone), and see what other colors they combine with them - obviously something with coral could be nice. I would look for one nice piece of art the next time you travel - it will then mark your trip, and remind you of something you had fun doing - again, ideally . . blue grays and earth tones in the art. Faded denim slipcover for an armchair would be a great starting point for seating, and you need a coffee table. One of those bleached out tree trunk coffee table bases might echo the wood tones / bring them onto that side of the room. Must advise sofa table behind (stone and wood top would be great / shelves with baskets) with lamps so you don't have to use the overhead. End table near window could be small and low. Gallery walls require artistic talent so if you are hesitant, it is easier to select a very large piece of art than to tackle all the elements and layout of a wall. If you head that direction, consider using sepia toned photos only, and interspersing them with some soft blue graphics in all metal bronze frames with dark chocolate matting for unity. Back with fabric ideas for pillows. Something ceramic and denim-y tones / wood branches set in that kind of vase would be great on the mantle in front of the large mirror. You want to lessen the mass of the mirror by layering just three things in front.

Since you aren't big "art" people, have you thought about a large mirror that would make a big decorating statement? Or you could always make a "family photo" gallery. Use matching frames (perhaps black) and do a series of about nine photos in black and white. Also, you could bring in some color with some nice silky drapes. How many windows do you have in this room? I see one, are there more? Are you thinking about re-doing the fireplace -- you could bring in some color by using some updated stone work. It is fine as is, but if you are planning to redo it, you could use more of the brown, beiges, grays, etc. Also have you decided on what kind of coffee and end tables you will be using? You are already off to a great start. I love the rug you have chosen. Is your style more transitional? That's what it looks like to me so far.... I would think about some silky drapes in the blue of the rug and use some blue and coral throw pillows. It will "cross-pollinate" the colors from the other rooms.

Here's one you might like for pillows - be cautious that you stick with straight blues when you shop for textiles, and not to veer into the blue-greens. http://beautifulfabric.com/asccustompages/products.asp?fav=0&fpage=1&page=1&categoryID=87&productID=7679&pStart=0&recNum=45
If you back fabric pillows with sensuede, they won't slide off the leather sofa.

A dramatic and large black and white framed photo such as Ansel Adams work would punctuate the wall.

The leather sectional is cold, needs to be warmed up with pillows. I would put a sofa table behind the sectional and lamp it. This way you won't have to use the awful ceiling fixture. Since your not into art, choose sculptural pieces. They have depth and dimension, and aren't flat on a wall. Easy on the print art with thin frames, looks cheap. Good luck!

Thanks for all the great ideas! Can you explain more about what you mean when you say to layer 3 things on the mantle in front of the mirror?

An odd number of things is more interesting . . like, a tall denim ceramic vase with a willow branch, one architectural wood carving fragment leaning against the mirror (dark brown to take down dark brown over there - do you have an architectural salvage store in your town?), and a mercury silver object layered in front . . . the things will reflect in the mirror (since I'm pretty sure from the layout it isn't reflecting the outdoors or a window / light or something really pretty now) so use it to add visual depth to the room / something tall , something square-ish /, something round-ish . .

Maps are another good way to fill space.. Constellation maps, geography of your area, or of sentiment to you are all strong looks with little fuss, and can be tinted.
[houzz=][houzz=]

Behind sofa in the corner some standing lamp in silver to reflect light floating shalwings in ivory. With blue and grey colour scheme oranges, chocolate brown, deep yellows and of course add some texture. Mirrors are also great solution for your room.

If you wanted a photo wall, a display like this might be nice. Pictures from a vacation could be nice enlarged in BW and framed. Photoshop can do many amazing things with photos also.

Hi! Here are a few ideas for you:

http://deciture.com/ik-catina-blue-embroidered-linen-pillow-w-down-fill/

http://deciture.com/ik-naledi-embroidered-pillow-w-down-fill/

http://deciture.com/morley-square-pillow/

Hope this helps you!