In order to avoid paying fees for images I (or others) use in seminars, I’ll often create my own. Here are a few examples:
Sometimes I need something bold, but photorealistic: Einstein is an example
Other times, I just need a simple animal design
Regardless, it’s best to think about the labor of the person who created the images. If you are charging for a seminar, please be sure to pay the appropriate fees to the appropriate artists. Otherwise, consider doing as I do and create your own.