A list of villagers I think are cute and cottagecore;
Fauna; cute normal brown deer
Deirdre; brown uchi deer
Poppy; little normal brown squirrel
Marshal; smug, cream colored squirrel
Beau; lazy, sweet deer
I agree with the suggestions above, especially the deer villagers who’d fit really well in a cottage core theme and Molly, Marshall and Poppy are all really sweet too.
Another squirrel could be Blaire, a smooth dark grey squirrel or maybe Cally. For a cub villager maybe Olive, the normal cub - they’re both cute and quite neutral colours to fit in with the theme.
Some koalas like Melba, Ozzie and Gonzo also have a neutral colour scheme (beige and greys) and they have a mix of personalities - normal, lazy and cranky.
Also think the dog villagers Bea, Goldie or Maddie could fit in quite well, they’re all cute villagers with quite plain designs and the brown and cream colour schemes would work well on a cottage core island.
I saw a photo of someone's island who had Molly, Maple, Fauna and Poppy and they did look wonderful together with their natural color schemes. Sylvana is another squirrel (or ferret?) who would work. Her house looks cute tucked into the woods. When I had a more cottage-ish island, Felicity fit in well as did Vivian.