A month ago added some 20 pages to my site. Some of these are in first 12 results now but images on those are not even being indexed in image search. They should be because text around is descriptive and images are good size and quality and using alt.
My old images are still in image search, so I wonder why the new ones are not at all.
Image search indexing is often a lot slower than page indexing. Not sure why, but it just is. Part of the challenge may be that it takes more processing to tag images for keywords, and also for SafeSearch.