>>95927342
A lot of creatures can be found with art in the official bestiaries, so if you look at those you can usually crop an image out of the PDFs for use that way.
Otherwise, I actually personally use the AI image generators for some of the creatures, this image for instance is what I got when I put the official creature description for a Leaf Leshy into Bing's AI image generator, which served me well for the one session I needed them for.