Whenever I upload and use images set as "screenshots" in my CatalogItems, they will not show up in CatalogItem objects downloaded through UnityAPI. Images set as "thumbnails" work fine and can be retrieved in Unity.
This is troublesome since — for no apparent reason — Playfab limits CatalogItems to just one Thumbnail-type image. Even if the documented limit for images is 100 for each Item, this makes it useless as long as I can only use one of them.
In the example below, Unity will report an empty Images list from the CatalogItems object because there's no file set as thumbnail in the Playfab console.
