You can purchase door shutters for all size and shapes of doors rather than having to make do with a door dressing thats as close as possible. They are available in a huge range of colours and materials which will allow them to fit in with an array of décor. If you go for a neutral colour you will even be able to keep them if you choose to change the colour scheme in the room you have added them to. You can read more here.
Dont panic if your door is not a standard rectangular shape as even the strangest shaped doors can be fitted with shutters specially made for them.