What if you did something like this from Lantern & Scroll (obviously in a darker finish). Or just email them and ask their advice. They are awesome to work with!

Check out cable lighting it is awesome for situations just like yours the company I like is Tech lighting.

Hi Odette! Have you had any progress with decorating? Hanging a mirror could be good in terms of light reflection and making a space seem bigger than it is. I like your idea with the photographs and horizontal lines - I might add some adjustable spotlights to make a feature out of the photographs! For e.g.

I think something like these tiles from Tile Style (http://tilestyle.ie/all-tiles/tiles/alchimia.html) could look really fresh or perhaps the herringbone tiles? Not sure where you can source these though but I love them. Good Luck!