Since you can connect your account already on XenForo powered sites, I think that page should be stolen from their playbook. I think it'd be cool on the user's first visit every day (or more/less often), their connected accounts should be crawled and the option to copy photos/statuses/link shares/etc into the site's gallery or automatically post a status update as a profile post or a link share as a new thread.
"We noticed you shared this picture on Instagram, would you like to add it to one of your albums here?"
"Would you like to make this status your current status here?"
"Would you like to discuss this article/website you shared in one of our forums?"
I'm not sure how it'd work with profile posts and link shares, but for images you could actually just automatically add it into a private album and alert the user to do something with it if they want later.