How do I decorate nearly 30 foot living room walls?

I would suggest some open wooden shelving and plants above it.

I had a similar problem in my sons apartment.One HUGE blank wall in the living room. I just kept looking up "art things" on Amazon and then came across this!! Turn a big blank boring wall into something really special- not expensive...fairly easy to put up, and it will never hurt the wall behind it-- when you get tired of it, it just peels off like contact paper. This is not wall paper..and it is esp. "renter friendly" since it cannot harm the wall underneath. Its been up for 2+ years now-and still look gorgeous. I love the way the birch trees reflect back off the large mirror I hung on the opposite side.