So far, one of my favorite projects I've completed was pretty simple, just inserting different fabrics into embrodery hoops and hanging them on the wall. So graphic, yet so simple! Plus the fabric hoops were only $5 at a thrift store and the fabric I already had, so great wall art for only $5! (Sorry for the not so good picture. I couldn't get a good one without blurring the picture. The light in the living room is not really good.)
They take up a lot of the wall without making it too crowded or too busy. Also, to hang them, you just need a small hole in the wall so the damage to the wall is minimal. This makes this treatment perfect for renters. I got the idea from this post which shows gluing the fabric to the embroidery hoop. I wanted to be able to change out the fabric if I wanted, so I skipped that step.