On the Isle of Luna creatures should be limited to plants and wild animals that can exist naturally such as bears or swarms of bats. 
Ocean creatures should be common and found near the coast. 

Any combat that involves NPC's from the town must be non-lethal.
Ghost and unintelligent undead can be used in some situations with approval.

   Other islands should include creatures or monsters that match the environment of the adventure. 

Level appropriate RAW creatures from the PF2e Bestiaries are available with a few exceptions. Re-skinned creatures can be used if the original creatures stat block is not changed.

Creatures with the dragon tag can be used only if their alignment is evil. Additional creatures may be added to the Restricted Creatures List so be sure to reference it when designing your adventures.