I didn't because there was no social media back then (1990s!) But I have posted in the past about my DC achievements - and my own - and when DC graduated from uni, got their first home, when me and DH got a new home, and posted pics of our holidays and daytrips etc yes... Because I don't have family nearby, and some friends live afar too. So it's sharing with family and friends who I don't see weekly. And most people on my social media do the same. That's what it's for. 
I don't think it's tacky, but people are entitled to think that if they wish. And on mumsnet, the general consensus is that ANYthing to do with social media is 'tacky' and 'cringe' and 'attention-seeking.' 🙄
Also, whilst it's sad that some women are struggling to conceive, and have had m/c (I have had 2 myself in the past,) I don't think it's fair to say you are being inconsiderate/borderline cruel, to post scan pics/baby pics/pics of the nursery or whatever you want to post, because it may jar them and upset them. I know it's very sad to m/c, or struggle to conceive, but people can't be expected to live their life around other peoples feelings.
I mean what next, don't post pics of your wedding because Lucy's fiancé ditched her at the alter? Don't post pics of your 1st/5th/10th/20th wedding anniversary etc, because Sandra's husband left her and fucked off with his secretary? Don't post pics of your new house because Liz and Dave got theirs re-possessed last Autumn? Don't post pics of your amazing holiday in Crete, because Sharon and Steve's holiday was wrecked because they all had a tummy bug? Don't post pics of you and your mum on mothers day because some people don't have mums anymore?
My mum died some years ago - in the late noughties - and whilst I felt sad for a few years seeing people with their mums on facebook having afternoon tea on mothers day, and spending time with them, I didn't resent them or feel angry with them. It's not fair to expect people to have to think about every single thing they post, in case it offends or upsets someone.
You crack on @firstlittlebub Post what you like. It's a free country. If other people feel aggrieved by what you post, they can click the 'unfollow' button. And congratulations! 👶