If your walls are non-paint-able you may wish to add a large, coloured pin-board to your room. If you're lucky, your room came with one of these, but they are relatively easy to make and a savior when it comes to colour themes.
[header] How to decorate difficult bedrooms [title] Decide on a colour theme. [step] This may be a subtle theme or the entire base of your room. Most room decorating articles say this, but it is quite important, otherwise your room will look random and untidy.