I think that you need mostly white, but something in a print that incorporates your colors. Perhaps pillow slips or at least a mostly pea green painting/poster/wall-hanging that also has some brown, perhaps in the frame. You could also do a stencil on the pink wall using the green paint, some white, and some brown. How about a nice tree branch? You can also buy vinyl decals from Etsy or other places--not sure that you could get pea green, but brown and white should be available.

You could also bring in some texture with bamboo sticks or decorative branches and help balance a bit the height of your room with small scale furniture. Spray paint them if you find the perfect size and shape but they aren't the color that you need. Ikea carries white decorative stalks for a very good price. the ones in the 1st picture hold well with small kids around and you don't need a vase for them. there are washi paper or crinkly paper floor lamps with a soft beautifully diffused glow For a budget friendly version check ikea or target http://www.ikea.com/us/en/catalog/products/80028552/

A houzz contributor, not too long ago, had made a wine rack out of 4'x4' wooden pallets, that are used in the US to move a load of goods with a fork-lift truck. Perhaps they have them in your country. He cut them in half so they were only two feet deep and stacked them up to high counter height. The wood would be a nice contrast with your concrete, might add a little warmth to the space. cascio.offsite@gmail.com

If you can't clean up the painted edge, you could always add a 1x3 piece of wood as molding. You can even carry it up to the ceiling to frame that wallpaper. I don't see that paint color in the wallpaper, or maybe it's a lighter version of the flower centers. Maybe stencil on a design using the darker color, or another color from the wallpaper to help tie it together. Then narrow floating shelves or vertical frames or something in the painted areas it you feel you need it. Maybe turn the bed around so the wallpaper is the headboard.