I went and revisited the 3rd dev diary again to seek out some specific things I noticed related to the pirate and generic themes that do not yet appear to be in the Alpha. Bear in mind I don't have access myself as I am eagerly awaiting this year's Nvidia GPUs. I'm enjoying countless youtube and twitch videos of others playing however so have to base my knowledge of current Alpha build content on those.
Here, look...
https://www.youtube.com/watch?v=maYufgvcRis&ab_channel=PlanetCoaster
00m 23s: A huge pile of gold coins (beside the treasure chest which
is in the alpha), different style of ride entrance.
0.26s: A pirate themed bench (two barrels with a blank between them). You can spot this close up in the pre-Alpha live stream Q&A with John Laws.
0:58s: You can see the pirate wearing a barrel from the pirate band on the roof as a standalone object.
1m 11s: Larger animated wall cannons (?) than the ones I have seen in Alpha videos, skull lamps on the walls of both buildings, benches in front of the building on the left.
At 2m 05s: those skull lamps again hanging on the walls, a different ride entrance arch in background, pirate themed chicken burger sign (chicken burger stall is not yet in the alpha either).
2m 30s: More benches, a dual circular street lamp I have not spotted in Alpha videos, bins/trash cans. Another type of ride entrance arch in the distance (white stone with a blue track piece beneath it).
2m. 42s. Those skull lamps again, and a pirate themed food sign hanging from the building,
From Twitter on 5th of March, art and render for a pirate and colonial soldier animatronic characters:
https://twitter.com/PlanetCoaster/status/706139923330498560
It is certainly possible some of these items have since been abandoned and what footage we saw prior to the Alpha release featured objects and designs the team might have simply been trying out, but I am quite confident there's more to come from the themes people are already having an opportunity to play with.