Hey guys,
I think it would be really complex to determine if the use has then switched / updated a photo and there's no real way to "verify" the integrity of the data if the user has already been migrated and he / she updated a photo / cover.
Take a look at this scenario for instance:
1. EasySocial migrates the user's cover from JomSocial -> EasySocial, the cover file gets a new name etc etc.
2. User updates his cover in EasySocial and the cover file gets a new name etc etc.
3. Now, if there are some issues with some of the covers, this would be problematic. There's no way to determine the "differences" between part #1 and part #2. We will never know if the change was by the user or the migration process.
If the cover issue only affects like 1% - 5% of users on the site, I would just suggest them to re-update their cover. It wouldn't take 10 seconds to upload a new cover and it gets less complicated