Are the preview image urls from kraken "Get Stream by User" static / permanent?

API
2

The previews are fetched from “https://static-cdn.jtvnw.net/previews-ttv/”, so yes they would be static images.

The URL for previews is,

https://static-cdn.jtvnw.net/previews-ttv/live_user_{username}-{width}x{height}.jpg