I don't think there is any backup option out there which can do what you are hoping can be done. The one exception is if you are manually extracting the data to be restored, and putting them in different locations. I just say this so you don't go feeling like this is some sort of weakness of Cloudron. Backups rely on timestamps and exact conditions. You couldn't restore the second backup because it would look for the time slot from which it was built, in the records, and those records aren't going to be in the currently restored backup. But if it is the media you want, then the fact you do have separate sets of backups does mean you can at least navigate through the backup and find that media, and then as @nebulon said, manually add them back to your Mastodon. But I gotta say, why do you need to have this media? I mean, Mastodon IS social media, and it's meant to be ephemeral. If there is some info you like, then screenshot it, or click the link and bookmark it, print it out to PDF, or follow the poster (to then check them out post-restore to see that specific post) etc. But saving it and keeping it to be viewable only within your Mastodon seems like a use even Mastodon wasn't really meant for.
Anyway, good to hear you are back up and running. Hope the new year remains happier. I'm @email@example.com if you want to expand your follow/followers!