Election Day PSA: It’s illegal to share photos of your ballot online in many states. Here’s why.
I’m quite sure those laws are for sharing them at the polling place. Those laws have never been enforced because they are almost surely unconstitutional. I have a hard time believing someone would arrest me for scanning my ballot at home and sharing it.
Ballot selfies should not be necessary. When casting your ballot, you should get a receipt with a unique identifier showing how you voted. Using your receipt's ID, you should be able to call up your ballot on a state database. Just so you know your ballot got counted. Just to remind yourself that you really voted how you voted.
While it's true that ballot selfies can be used to validate vote-buying and enforce voting under duress, those are crimes that must be prosecuted vigorously!
But balance the threat of that against the reality of an instant, crowd-sourced recount!
I.e., if no one complains, then the count is accurate. If someone yells, "My vote isn't there," then investigate.