There is a web site that contains images of church book images across mainland Europe, mostly in Germany and Austria but also including Poland, Netherlands, Hungary, Bosia-Herzegovena, and Luxumburg. The number of parishes included is amazing. The current count of churches included is nearly 6,000. This site is known as Matricula Online. It can be found at https://data.matricula-online.eu/en/ . If you have ancestors from these areas, be sure to browse their church book image collection.
I looked for churches my family is known to be from and sadly, none of them are there. I'm still excited to find this site. They state that their goal is to continuously expand the content of the site.