If you're competent at hanging wallpaper, or know someone who is, create a spotty wall behind the bed or in an alcove. Try Harlequin's neutral design for a casual finish in a nursery or go bold with gold glitter-effect spots from Spoonflower...my favourite!
Probably the easiest option of them all...and the least messy!!!
Again, you can either buy them ready to stick to the wall...or try making them yourself...