Tattoo's

So I have a back tattoo of a Bird with a red sun and tropical foliage, I'd like to eventually do my whole back and down to my butt! I talked to my husband about eventually doing that and he said I'd be ruining a good part of my body. And it wouldn't look as nice. (i have my whole left arm, leg, chest and half a right leg tattooed and he never had a problem with me doing that.) He knows I like tattoos and he himself has them and I support him in whatever he wants to do. I was caught off guard when he said that, because he doesn't care what my hair looks like or how I dress but he got upset over my butt being tattooed? I'm kinda lost?