have you heard of these http://www.ussunlight.com/products/skylight-tubes

You could add a high transom window on a wall in the room that backs up to an adjoining room and share the light from that room.

I belive if you create your space using lots of white with splashes of lilac and grey the green background will become secondary.

Just a code/general construction question...how is this considered a bedroom without egress? All code bodies...everywhere in the US and in many other countries...require that a bedroom have a direct exit to the exterior of the house. Windows must be sized appropriately and doors must exit onto a legal platform. No amount of decorating will solve this problem...I am surprised that it escaped the home inspector when you purchased the home. Of course all this is moot if the home is in a country that doesn't have a building code. Best of luck with the design!

Little off topic. This used to be called a den. a scary trend that is happening especially in condos is that these windowless area are being advertised as a 'bedroom'.

Consider using opaque doors if privacy isn't a major concern.