If the window/curtain has this tropical wallpaper, then I would suggest to go to plain matching colour. If not, try to match the curtain pattern to the wallpaper one, like in this example:

Do you have a picture of the room and paper?

Is it the dark or light background?

its the light background sarah l x

Are you papering all walls, or a feature wall. As Cotterpine says, use plain curtains if the window wall is papered.

I'd go for a plain dark colour! getting too many patterns involved will look messy and completely ruin the room

i will probably paper all walls, in the pattern but not 100% decided, we may swap the paper for a plain one once feature wall done. I duidnt want to go down the plain green curtain route though.