I have used undraw.co and the pictures are numerous, clean and customisable. It is an amazing piece of work for anything that is monarch-free.
unDraw has been in the works since 2017 and is maintained solely by Katerina Limpitsouni. Since launching her open-source illustration library, Katerina has designed more than 500 illustrations in any category imaginable.
Personally, what makes unDraw so appealing is that you get copyright-free SVG files, and you can also color manage the illustrations directly from the website.
By having access to SVG files, you can edit, customize, and stitch together multiple illustrations for a thoroughly custom design.