No one at the company provided any more details any more details on the Facebook post where they have mentioned this new feature (and shown the screenshots below), I think it's safe to say that it should be a new kind of autogen (auto-generated) parts in which small details are added to the scenery.
On the screenshots we can see things such as mailboxes, swings, benches, picket fences and even a sandbox. Now, although it almost looks like an April's fool joke, there's no reason for us not to take it as a serious feature coming up with the next update.
I have reached out to Laminar Research and am waiting on more information about this cool feature.