Yes and it is beautiful in B&W, I just tend to see colored art especially when it reflects this kind of warm emotions like the one in this picture ^^ Kind of childish feeling that likes to see thing in color hahaha
Humm, the background? You're right about the bigger sheet, it will turn off the focal point you achieved, also detailed background will do the same! I don't know about the plain BG, maybe if it's styled in gradient it won't look plain?
Yet, there's another way but I'm not sure if it works with this piece. In one of my comic episodes i just painted blurry BG for my panels, it contained bushes and people figures and other stuffs......you can check it out as I'll provide a link with my latest upload to a video of the coloring process that contains notes on the BG coloring at the end of it...if you wish ^^
And good luck with your redesigning work Gytrash