My top three still stand the same.
1. Pirates! So many fun theme ideas could be had! But I am also biased, I just want more ship/pirate theme items and pets.
So many ideas could be made; magic, sea shanties, treasure(jewels, gold, doubloons), attire & weaponry(imagine naval uniforms or pirate captain coats with all the fancy regalia~), Davy Jones, creatures!(I would love some sea serpents, krakens, whales, sirens/merfolk, etc.!), backgrounds ranging from various areas of a ship; captains' quarters, brig, below deck, upper deck! maybe other ships like fishing or naval vessels, there is so many different types and sizes of ships like galleon, brigantine, man o' war, etc.— there is so many tales, folklore and mythological creatures that could be had.
2. Norse Mythology/Vikings! Again, I'd just love more viking/ship items and pets, but imagine the runes and weapons and various inspirations to different myths and gods. Backgrounds could range from nature-y, to maybe Valhalla and the like.
3. Greek Mythology! Like the above, though I want the above a little more, I would still love to see items and pets based on it. We have a Hades pet from the 2020 Halloween event, we need to rest of them now. XD *totally don't just want greek god pets to make a group for EPIC dress-ups*.
Honorable mentions that I would love to see too, but not as heavily as the above; Events based around Japan or Arabia cultures and mythologies, respectfully. Or a steampunk, Victorian, and dystopian themes would be awesome too. Could even be all three in one, as it could mesh well and give a wide variety of items and pets to explore~ I'd love to see flying airships, victorian apparel, etc.