My folks wouldn't have the first clue about skype/facebook etc., and it would have been a BIG ask to expect them to bend over backwards for the one daughter who could't get there, when they were concentrating on their other daughter's big day.
I would put this behind you. You couldn't attend, and therefore, with that decision comes the knowledge that you won't see your sister walk down the aisle. You can be upset of course, its upsetting, but if you start saying "couldn't one of you at least posted some pictures or skyped me?" they'd be well within their rights to say "couldn't one of you afforded one plane ticket if it was so important?".... and that would just get messy.
I went to my sister's wedding, I had a horrible day, my sister (usually lovely) was downright rude to me and made me feel pretty unliked, and I cried a lot... but there was no need for me to kick off, it was her day... I've said since that I was hurt by her, and she's accepted it. So maybe, what needs to come from YOU is to keep saying how gutted you were that you missed her wedding, that you wish her well, that you miss her in general and that being an ex-pat is harder than you thought it would be. Your family will respect you more for that than if you start having a tantrum.
Your sister probably missed you massively, but seriously, expecting everyone to take a fair old amount of time out of their day to skype you, post photos etc., especially if that's not their thing, is asking too much.