Look at my city art prints. They fit the cool theme. Or for something more traditional look at the limited edition painting prints on the same site. You can find them on printspace.com.au

I would suggest hanging a large moroccan woven fabric or mat, just use a length of dowel along the top edge, and hang it up. It would add great texture and also a casual feel to the room. Dress up the couch with a bunch of patterned cushions and a bolster moroccan style. A silky fabric sun filter curtain would finish off the look. https://nz.pinterest.com/pin/299911656409300053/ https://nz.pinterest.com/pin/405675878916401870/ https://nz.pinterest.com/pin/431219733049382426/

If you have a small powder room, then you don't need art work. Don't just hang art on the wall as you have a blank wall - negative space in a small room is a positive. I would consider a decorative mirror with bevelled edges to provide some visual interest, to make the space seem bigger, and which has a function. Consider wall lights to complemement the mirror, and don't go with the plain jane mirror option that most builders offer as standard. Best of luck, Dr Retro of Dr Retro House Calls

I think some shelving would look wonderful, keep the styling quite simple so that your eye doesn't get pulled away from the TV when you are trying to relax. A couple of floor plants either side of your entertainment unit would keep the electronics company and finish off the look quite nicely.