Oh, is it because the IDs you are inputting are a decal? Use this solution a Roblox Staff posted if you want to convert the decal to a Image because the Image property has to be a Image not a decal.
EDIT: this will only work for ROBLOX’s (UserId: 1) assets sadly, there is another way to grab the Image, (MarketplaceService.GetProudctInfo, and inside the table look for “IconImageAssetId”)