Look through the houzz idea books for inspiration.

I've been looking through them but haven't found many examples of such a large blank wall without windows or anything else

Use the search option above and type in decorating a large wall. It will show other threads where people asked the same thing. It's a starting point.

I suggest a row of 4 prints above the sofa. It's okay if there is "extra" space above the prints. Notice these aren't huge pieces on a large wall...

Family collage :)

http://houzz.com/photos/2403559

http://houzz.com/photos/2279812

I think the layout is the problem. Why not bring the couch to face the fireplace? Then I would find an interesting sideboard of some kind to run along the wall to anchor it - then you could put some interesting pieces on the sideboard - with some height to them, as well as some art pieces on the wall.

I think your sofa is too large to put anywhere but where it is. Plus, it's great for tv viewing. I'd suggest an accent chair in the corner in front of the cat tower to round out the sitting.

Thanks all! Yeah the couch is way too large to move from where it is.. For this room comfort is definitely key. I like the idea to add a word like family on the wall to take up some space and break up all the sharp lines I already have going on in this room.. Which is why I want to stay away from just hanging some more square picture frames up. I definitely want to add an accent chair or two on the other side of the room as well to help balance out the couch on the one side of the room.

I would add a map of an area you love. I make maps that are one image made up of different size frames landscaped 75% of the area. something like the Florida pan handle through the gulf coast of Texas. Don't have a picture right now as I am headed to the lake but here is some of what we do. NostalgiaFineArt.com

These are a few ideas that I liked. . .
#1 floating shelves where the images can be easily changed out.
#2 canvas collage of family photos
#3 family tree wall (just a warning, I've seen them done very nicely and some that look awful)
#4 is a customizable vinyl wall decal from Etsy.

Please don't hang a bunch of stuff just to fill up space. Whatever you put above the sofa should have some unifying factor. And there is nothing wrong with hanging up square pictures if the pictures themselves are compelling.

While I'm not a fan of family pictures in public spaces, it can be done effectively. Here is my favorite use of family pics ever:

BTW, I would also like to see your rug centered on the fireplace, even if it means the sofa feet don't sit on it. The way it is now just looks off.

Are there two t v's in the room? What is over the fireplace?

Maybe a water wall? Check out more at: http://www.luxewaterwalls.com/

I always love the eclectic style in using many frames of differing size. That may be your best option as the wall is quite long and skinny so it could be difficult to find two or three bigger frames that would fill the space correctly. Good luck with the design.