I'm not sure if there's an alpha 20 seeds thread already or not, but here's my top three so far. The preview images have a suggested base location which is scored based on prefabs within 1km of it.
Version: Alpha 20 b218
Seed: NumidiaCambist
Size: 8192
World Name: West Gojuzi Mountains
Pros: Almost all downtown buildings and 3 traders within 1km on suggested base location in the desert biome (increased loot stage).
Cons: Only three unique tier 5 prefabs in the whole map.
Preview: https://imgur.com/Y8BNo5h
Seed: OccidentalistBetaine
Size: 8192
World Name: Xeruye Mountains
Pros: All but one downtown building and 2 traders with 1km, split forest and desert.
Cons: Least amount of unique prefabs among the seeds I generated.
Preview:https://imgur.com/Y84mJqr
Seed: CastelessCygnets
Size: 8192
World Name: Riciyuco Territory
Pros: Five tier 5 prefabs and 2 traders within 1km, on snow.
Preview:https://imgur.com/F2w1JaX