I have an idea for a new theme.
"Open sea and rivers"
contains: placeables and creatures to be found above the sea/river surface, ships, boats, vessels, rafts anything that sails, seafood, some new open water tiles, a sea skyboxes, swimming systems and animations, fishing systems and animations.
More specific examples: crashed ship remains (ship parts, cargo - barrels, chests), floating bodies (dead or alive), whirlwind placeables, kraken and octopus designed in way they fit the walkable water tiles, sea storm skybox, open sea skybox, sea cave tiles, cliff tiles, rock above/under sea surface tiles etc.
Its something I needed and couldnt find when I was working on the ship battle system, Ive done some work on the tiles but havent finished... yet.