@Ryonia it appears to be working when you use https://kagi.com/images?q={google:imageURL}&reverse=reference (source) as image URL (with empty POST parameters) for most cases, but as you said:
Kagi may not have access to the url and the image stored there.
Which is indeed the case, and eg. searching for images from reddit (on the post list, not in the post details) will yield no results (eg. for this post preview URL is https://preview.redd.it/somethingaiwillneverreplace-v0-c9958wjwnv3d1.png?auto=webp&s=83184ccbc4522446bce29c6ee658e944559efa72 and using it in search gives no results, but after going into post details the URL of the image is https://i.redd.it/c9958wjwnv3d1.png , and using it in search does return releveant results)
