If you're a fan of websites and e-learning courses that use illustrations, unDraw by Katerina Limpitsouni is a useful resource. According to her website, unDraw is "a constantly update collection of beautiful svg images that you can use completely free and without attribution." The open-source illustrations can also be uploaded in png format.
My favorite feature is the ability to choose the main color for each illustration. This helps to match illustrations with a client's colors.
unDraw also comes as an Adobe XD plugin.
For anyone interested, I have a personal blog titled My Journey to Know the Savior where I share reflections about Jesus Christ.