I love the simplicity of it so far. I assume you can't paint the walls? If not, I think a photo collage of framed photos in all different sizes would look great above the bed. Or, maybe some simple plank shelves.

Wall decals might be something to consider:

Why not bring the black over from your dresser top with a collage of picture frames hung on those removable hooks;) I also love the decal idea as they are also removable and fun!

I love your bedroom, so simple and soothing! I would go hunting for something that speaks to me : either art or other wall decorations.
Here are some ideas
mirrors, starburst, frames, original art
http://www.wayfair.com/Square-Mirrors-C539333.html
http://www.homedecorators.com/newThumbPage.php?classification=5&typeDefId=12172
http://www.homedecorators.com/P/Portia_Wall_Mirror_-_Set_of_12/250/

Your restful room reminded me of one of my inspirations. Curtains and some subtle artwork will complete the look.

The simple and inexpensive thing to do would be to paint the wall behind the bed an accent color.... You could promise the landlord that you would return it to the original color when you leave???? OR, if that isn't an option here is another idea using a beautiful folding screen

You could also do old barn wood frames in different sizes. They sell them at hobby lobby and Micheals. Usually on Mondays they have discounts of their framing at both stores

this

f the landlord allows paint the sage green and gray actually enhances your space!
(Nicely done, Spacialists)

I agree with bringing a darker tone to this side, but don't think you need paint. Some rigidity in structure will help tie the more masculine lines of the dresser to the curve of your bed:
http://cdnll.touchofclass.com/images/xxl/Z861-001.jpg

Wall Decals are the best way to do something with your room, Because it is the only option which is the most attractive and alluring way to inspired your friends and visitors of your room.

Try some wall decals from bannerbuzz

Wow thanks so much for responding! Still experimenting over here. Will create a new post regarding the old headboard(just needing a quick fix until we get a new one in a few months) my OCD is extremely bothered by what it looks like now! Lol. Thanks once again! Our first place is making progress day by day thanks to all of you! I feel a before and after album coming on..:)

If you can't paint the walls, find a beautiful fabric to put on the wall with starch. It removes easily. Updated your pillows on the bed with a print that coordinates with the fabric on the wall.

If you are not attached to the headboard, I would make the headboard to be 6ft. I feel king beds look so wide, that this brings a nice height to the room, and also makes the room look larger. Flank the headboard with 2 long mirrors (rectangular or oval venetian). This will also give the illusion of being larger.

I agree with Chemayne, those painted walls look beautiful, but I guess as you are renting you are unable to paint. So maybe a large long frame with you favourite wall paper in it. Looks great and adds colour with out and wall damage. then pick up your favourite colours from the wall paper in cushions and vases flowers etc.Or just some black and whict and maybe grey wall paper and cushions in colour,check out my facebook page essentia interior design for some cushion colours!

Family photos, wall art, or even a new big bed head would do it.
your room is lovely and modern I like it.

I would even go with a charcoal grey to give a more dramatic look. Love the simplicity

and definately white soft fabric curtains

Or a piece of fabric, hanging straight down a pole above your bedhead:

I love the idea of some retro black and white artwork to go above the bed. You could use different style and size frames, paint them a black or neutral colour and fill them with pictures of black and white celebrities, James Dean etc. I think there's a sale on at Fab.com for those and I'm so tempted to get them myself. If your landlord would allow, you could also consider a muted tone wall mural behind the bed. I bought some fantastic newspaper and brick wall ones from Tangletree.com

Sorry, my above comment meant Tangletree-interiors.co.uk. Sorry if you're not in the UK!

I also like the idea of wall decals or peel and stick wallpaper. Since I live in earthquake territory, I wouldn't recommend any heavy pictures or mirrors behind the headboard or next to the bed.

I suggested this 3-mirror solution to a similar dilemma here at Houzz and it looked great in her room. Do it in the black to match the mirror. I attached her after pic for you.

A simple long mirror.....keep the bedding light and airy...