I think it's a great piece. Personally I think you should stick with the black and grey for this style. It's timeless, beautiful and will be easier to match with other tattoos in the future. Regarding adding a background, I think you could look at the work of Tamara Santibanez, Kane Trubenbacher, Spider Sinclair and Ruby Quilter for inspiration. They all create fineline black and grey work and they have work which is made up of several elements (like a back) similar to the style of yours. They also often add background detail which is very soft and beautiful. I also have a pale complexion and I have several tattoos which came out a little darker than expected and initially wasn't happy with but love them now. Yours already looks like it has softened a lot and will only soften more with time. Take care and enjoy your lovely piece.