Open Archives makes various collections of archive institutions and historical associations easy to search. These collections also include various prayer card collections.
Open Archives also publishes prayer cards from private collections.
Do you have prayer cards (or memorial cards, or death cards) in your own personal collection? These can easily be published on Open Archives!
Add your prayer cards - the scans and the information - to Open Archives so that other researchers can also benefit from this.
Find your ancestors and publish your family tree on Genealogy Online via https://www.genealogieonline.nl/en/