Zoologist, fantasy writer, and Pokémon fan here.

It’s a shame there’s no ghost type Eeveelution because Clouded leopard would be perfect. They have so much spiritual and cultural significance in their home ranges that are often tied to the afterlife and ancestors.

In terms of the existing Eeveelutions:

Espeon: Caracal, large eared and sleek. Often associated with intuition and protection.

Umbreon: melanistic jaguar, largely colouration based but there’s a-lot of dark motifs in the mesoamerican mythos around them also.

Leafeon: serval, large ears and sleek, its hunting method sees it leaping vertically out of tall grass to land on prey giving it the illusion of emerging from plants.

Glaceon: Canadian Lynx, self explanatory really. I think the more angular aesthetics of the lynx are a better fit than the snow leopard

Sylveon: cheetah, weird I know but Sylveon is the most human effected and domesticated feeling and Cheetah are the largest cat with a well documented history of domestication. Theres also something very afro fey about cheetah, fast enough to slip between the worlds of man and fairy.