Unfortunately the room is completely upside down at the moment (wardrobes and other furniture dragged to the centre of the room so DH could gloss the skirting boards) so it wouldn't be a very clear idea of what the room looks like.
My friend has this, but not as wallpaper, hers is one of those giant stickers to go on the wall. It is basically a tree with all the little birds and bird houses etc. It looks really lovely. She did it with one pale green wall with the sticker on it, and then the other walls are cream with little parts of the pattern (I think there was a branch with one bird, and then a row of flowers) It loks really nice, reading back what I have written it sounds a bit twee, but it isn't in real life.
I'd say a very pale green too, it looks so fresh with white skirting and also would go well with your dark furniture? It's beautiful paper btw. We did our nursery in pale green and it is quite easy to update when they get a bit older- we had boys, but went from green and animals to green and dinosaurs in a day!
I like the green idea too. Although I wonder if it's going to be a bit busy with dark furniture as well, so maybe a green and pink room (even F&B French Gray would look nice) with the wallpaper used just as framed photos as a PP suggested? That would be a lot easier to change with age, too.
The house we bought came with what we used as the nursery already decorated. Three walls have some flowery wallpaper on, sort of like this. The fourth wall (the one with the window in) is painted plain blue to tie in with the wallpaper and I added cream curtains.
I think for the wallpaper you have chosen I would either: decorate three walls with it, then paint the final wall cream with the pink curtains you linked to. Or paint three walls a colour to match the curtains you linked, and use the wallpaper on the window wall. I think the furniture will be fine, it will offset in the light room.