Oh, this is really nice. I like that it's a simple composition, yet well put together. I think it's the diagonal lines of the figures and the bed that keep it looking interesting, as well as the contrast in darkness between the bed and the figured and background. Also that the the figures and background are painted in subtly red tinted colours. It's not a glaring colour contrast, but enough to distinguish. :D
(Sorry for going all theoretical here ^__^;).

Besides all that, it's alltogether a very lovely picture ♥