This post is to help me in the future! Here is the list of links which provide the list of tags which are available for all the Azure App Service Docker Images.

While building the images for Azure Web App for Containers, I have had best results by building on top of the images which Microsoft uses.

Python - https://mcr.microsoft.com/v2/appsvc/python/tags/list
PHP - https://mcr.microsoft.com/v2/appsvc/php/tags/list

I will add more as I find them. You will have to search for the latest tag to ensure security updates are applied.