Some of the sources for images I use (all free use or public domain or cc by at most ca). Other images from my phone.
For example, the Rotten Banana in the shop was sourced from Nastassia Ustyan on Unsplash then edited for here.
More sources
Openclipart Constantly being added to. The post image for this on the home page is from there.
http://www.clker.com/ A lot like openclipart.org with more ads.
publicdomainvectors.org/ Even more clipart.
Pexels Superb all PD photos and videos.
Public Domain Files Big variety but not huge numbers. Always worth a look when wanting things that are neither clipart nor photos.
Unsplash Photos and videos, varying quality, lots of them. Lots of istock pay photos buried in it, so careful what you click.
Illustrations Quality free clipart, more detailed and current than almost anything else. Can get svg versions which are infinitely scaleable like this one:
Undraw Presentation quality Clip/icon art with ability to recolor before downloading, images are your choice of svg and png.