I think wallpaper is going to be too overwhelming. The rug is such a great statement piece that you don't want to take away from it. If you were to go through with wallpaper, i would say no colors, and a very muted pattern. If you want an accent wall, I think texture is the way to go. If you look at some of the photos in this gallery you can see how wainscoting was used for texture. The photo I think makes my point the most is the bathroom one. If you were to do a full wall of wainscoting like that, matching your walls (or white if you want) it would make a great accent wall and support the rug as a statement, not take away from it.

I like wallpaper, a lot. But, I do not see where you could add it. You really don't have an isolated wall.

I suggest a more vibrant canvas on the wall, and definitely, different throw pillows. Those things may give you the same effect as an accent wall.