I might be in the minority when I say this, but I personally think any art that's created to be public domain deserves to be more loved and appreciated for the work that goes into them. I know people tend not to think much of clip art due to the fact that their position in the public domain makes it easy to take them for granted, but the artists and companies that make them do put in the talent and effort to make artistically good images. In fact, here are some great websites to get clip art from:
https://www.gettyimages.com/
https://www.istockphoto.com/
https://depositphotos.com/
https://www.dreamstime.com/stock-photos
https://www.shutterstock.com/
https://www.illustrationsource.com/
https://www.vectorstock.com/
https://pngtree.com/
https://www.picgifs.com/
https://www.alamy.com/
https://friendlystock.com/
https://www.ikon-images.com/
https://creazilla.com/
https://openclipart.org/