A small part of the 2017 manual salvage and mapping work of members with salvagable images on the forum has consisted of hunting down official GW/FW artworks. This was critical for the FW LoA sketches, which almost only existed in a single Photobucket album as far as I could see (with a few duplicates hosted on DakkaDakka).
It was a relatively small step to try and hunt down all official CD artworks ever put out. I hope this is exhaustive. If you find more official artpieces, then please shout out!
Google Drive Album
CDO Staff Imgur Album
Here they are in somewhat chronological order:
Age of Sigmar Fyreslayer Art of Interest