My youngest son noticed this and I don't think anyone else online has mentioned it yet. Take a look at the opening shot from the finale intro. On the right, there's a multi-faceted icy sphere.
Adjust the levels a little bit and it becomes very familiar:
Clearly this is the self-containing time capsule of Patience St. Pim, last seen in the episode Skyhooks 2, suggesting she'll return in a thousand years (which adds up to the setting of the finale intro)!
