I suppose I can see what is happening with the OP and her family; it's very different to mine because for a start, none of my extended family (which is small) uses social media. We don't post photos there at all, they're only posted between us on a whatsapp group. That is where I'm coming from and I haven't experienced the same issues as OP because my family operates differently.
My point was in relation to OP's daughter because it is so, so easy to cause rifts within a family but that said, family members shouldn't be sharing photos outside the family. I don't get it, what's to 'boast'' about even? A family baby is surely only special for those family members?
If OP's extended family are taking and sharing photos with friends then they're rightly not going to be provided with that opportunity in future. I read OP's first post and thought it was a bit 'gung-ho', a veto to family of "We have decided that none of you can be trusted therefore only husband and I have access to photos of baby", and wanted advice as to how to tell them that they weren't going to have photos any longer. If there were family members who weren't guilty of sharing photos around then I imagine they would rightly feel aggrieved, I certainly would.
I don't think the argument of 'consent' is much cop because if it is, OP shouldn't be taking photos either and it just sounds like a possessory thing which as a family member I would back right away from with no regrets.
Handling this so that it doesn't blast a grenade into the extended family is going to need deftness, not foot-stamping, not unless OP/husband are happy to estrange themselves.
OP, I wish you well with this, I can see where you're coming from but you need to really think about the outcome that want or are at least prepared to live with and work backwards from there. Good luck!