Here at Apartment Therapy we're big fans of the gallery wall, and have sung its praises at length over the years. But for renters, all that measuring, arranging and hammering might not be the most practical solution.
A better one could be the impact of a single, oversized piece of artwork — nothing brings a white wall to life faster or more completely. Take inspiration from these rooms, all of which use the "white walls + big art" formula with aplomb.
TOP ROW:
1. Kathryn & Perry's "Have Less, Do More" Apartment Tour
2. La Dolce Vita
3. The New Design Times
4. The Diversion Project
5. The Diversion Project
MIDDLE ROW:
6. The Veda House
7. Heather's Bold & Blissful Bozeman Home House Tour
8. Ixxi
9. The Marion House Book
10. The Craver Compound House Tour
BOTTOM ROW:
11. Emmas Designblogg
12. Christine Lane Interiors via Apartment Therapy
13. Mikel Irastorza via Houzz
14. Alex & Alina's Lovingly Layered Home House Tour
15. We Heart Home
(Images: as linked above)
Apartment Therapy's Sofa Shopping Guide
Nikki’s Sweet and Cheery Print Studio
Good Food to Share 
The Big Book of Small, Cool Spaces 
Apartment Therapy Presents 
The Eight-Step Home Cure 
Sprout Side Table
5 Things Paris Taught Me About Travel
Recipe: Ham, Cheddar & Chive Egg Bakes
I am absolutely in love with that Tony Scherman painting in the Marian House. Sadly I can't afford $25 grand, so I'm going to buy my own canvas and try for something simular.
similar that is...
Works on coloured walls, too! Go big! :)
http://dodiegoldney.wordpress.com/2013/02/15/procrastination-and-perfectionism/
And down near the bottom of this post - that's my own work in housepaint on plywood:
http://dodiegoldney.wordpress.com/2013/03/10/looking-at-the-overlooked/
Interesting, no quilts. When I was a quilter I used quilts to add color and noise reduction too. Then, I'm a quilter and have a lot of quilts.
What! That ixxi company is amazing!! It's like a slicker and easier Rasterbator...with a less creepy name, to boot.
This is great advice for renters. I also think a big mirror can make an impact on a plain wall.
My favorite, not shown here, previously shown on AT ( that I cannot find to buy) is the R. Lichtenstein "I can see the whole room and there's no one in it.".
It is so great to see some homes in this post that look more like the "white" rental walls that I have. It is frustrating that a lot of AT's posts on white walls in the past deal with homes that are making white a choice. Unsurprisingly, those folks have not chosen the dingy white that even a newly-painted rental apartment usually has in it. These walls are tough, but necessary to work around for a lot of renters, so it is nice to see some inclusion of real-life ways that people have made it work for them.
And if you don't have a quilt a large piece of fabric is also a great option. If you make a hem along the top edge large enough to slide a bamboo pole through you can attach string to either end of the pole and hang it with one nail/hook.
@rmbnn here's a resource for that Lichtenstein print.
http://www.postercheckout.com/PictureFull.asp?PrintID=8634
Love the scale
TY Dulcibella, though I see it's 'out of print'. Drat! But, I'll bookmark the site just in case.
The cure for my white walls? Two large canvas prints, a mural, and a large art block from EyesOnWalls. Also a large leaning mirror.