In the anime they use a resource that is to add a lower lip to the girls, I suppose it is to denote that they are very pretty, that's why I used this resource with some girls.
For example, the “They Deserve It Too” mod adds new portraits to vendors who don't have one.
Leyalluna's Portraits (Content Patcher) is a modification that replaces all Non-Player Character (NPC) portraits within the game. The creator intends to develop a seasonal version, which will also include character sprites, as a future update. This expansion is noted as a significant project, meaning its updates will be released incrementally as the developer's time permits.
Claire Portrait is a Stardew Valley mod that adds a new character portrait for Claire, the overworked sweetheart from Stardew Valley Expanded.