You could start by looking into a shade such as the wall art or you may even add an additional lighter brown hue that works for you. Don't be afraid to play with colors that you are drawn to. Our recommendation would be to take a look at the Benjamin Moore Color suggestions to find a range of color that works for your design. Thanks for the question! https://www.benjaminmoore.com/en-us/for-your-home/explore-paint-colors

I am doing something similar, but really struggling getting the lines straight. What do you suggest?

I would purchase one of those straight line laser pointers with a leveler. You can purchase at your local hardware store. Have someone hold the line while you tape. Should help create straight lines. Hope this helps!

How does it look for accent high celling wall? Room is open concept kitchen living room. Kitchen cabinets are dark brown.

An accent wall with a stripe would look amazing in a room with a high ceiling. You could also do a wallpaper - this one is in stripe and temporary - so easily removed later: http://www.2modern.com/modern-art/wallpaper/wallcandy-stripe-temporary-wallpaper