Some of my designs are from original art, some use elements form historical documents, and some are from Doverpublications.com that I have bought their clip art books.
On each designs page, I try to give credit for elements I have used when it is required. Sometimes the POD sites break the links or they get lost when the website has been updated. If you see a link that is not correct, or you would like it changed, please contact me so it can be updated right away.
I always document at the time of use the license requirements of the element I will be using, be it public domain or creative commons. If you see one of your elements and have changed the CC licensing since that time, please notify me right away for me to update the crediting.
Below are some of my sources.
The Biodiversity Heritage Library