Great first attempt. May I suggest a couple of things ? First of all, during processing go into levels and move the left hand slider to the right, this will darken your background. You can fiddle about with the others until the contrast looks right. Secondly, take a sheet of silver foil and attach it to a piece of cardboard, needn't be too big (A4). This can be used as a relector to put some light into the unlit side of the rose.

Martin