I've always love Isak's Penguin wallpaper, but suspect it isn't really meant for a grown-up bedroom. However, I think their Lovebird Wallpaper could provide a suitable alternative.
The design consists of a repeat pattern of two birds with their tail feathers forming heart shapes. It is a sweet design, but the geometric style makes it that little bit more grown-up. It is also available in sophisticated shades – choose from stone or mustard. It is made from sustainable sources and costs £38 per roll.
Buy it directly from the Isak website, which, by the way, has recently undergone a fantastic makeover.