Facebook is a good location for engaging, unusual, and inspiring images. Not everything available has a credit line, but when possible include that. If you plan to publish your writing lessons to a wider audience, then having a credit line available will make that work easier.
On this page:
screen shots of how I organize my images
some quirky images
Start a folder on your laptop or devise so that you can save interesting images.
Create categories for them, which will help with quick retrieval. Examples are: animals, art, food, nature, people, quirky.
Categories will also help you assemble photos of a similar theme or focus.
Quirky pictures are engaging for learners. They are often surprised and "hooked."