https://www.roblox.com/Thumbs/Asset.ashx?width=110&height=110&assetId=1818 exists so that it is possible to get the thumbnail from an asset id, and GetProductInfo has IconImageAssetId for developer products, but there does not seem to be any way to get the icon for a gamepass since gamepasses have IDs separate from assets now.
I just realized this, that’s actually really annoying. I guess the only real solution upload the gamepass icons as decals
This has been filed as a bug internally.
Has this been fixed yet?
EDIT: The image Id is accessible