Easiest fix is canvass. You can buy them at Home Good's or TJ Maxx if you have one in your area. Here are a few I found at Wayfair.com. ( none will work with your Christmas pillows but all will fill the wall and add needed color and make a statement):

Here are some 60 X 48 inch suggestions. More at: http://www.houzz.com/projects/1295077/art-original-abstract-paintings

Art - Original Abstract Paintings · More Info

SOLD!!! --Original Abstract Painting 48 x 60 · More Info

Saatchi and Etsy, both original both under $400 many more too

Buy original Painting art and art prints online · More Info

Abstract Wall Painting expressionism Textured by xiangwuchen · More Info

I would look for a tryptych to cover a larger area if we could see rest of space we might get more imaginative

Can you post the size of wall on sofa back? How many inches across the back of sofa?

so gem, what say you?

How about a wall mural that is about 8'x12'. behind your couch?

Komar 100 in. x 145 in. Penthouse Wall Mural-8-916 - The Home Depot · More Info

Thought you could pick up some ideas from this boho-eclectic living room with a mural. See how they decorated the other wall. Love the large F! There are hundreds of different murals to choose from.

Decor Demon's Loft · More Info

You might like to check out our signarture online gallery: all our original artworks are very contemporary in style and if something resonates with you, we can definitely create it in the size and colour to suit: here's a link to triptychs (ideal for above your sofa) in warm orange tones:

http://www.signarture.com.au/collections/all/orange+triptych-up-to-3-0m