Springshare pretty much says is all on this page of their Getting to Know LibGuides guide.
A couple of key points are:
- Make sure to add alt text to every image
- Make sure your image is appropriately sized or re-sized for web (no more ~1200px for the longer side)
- Use a descriptive file name for your image
- Good: students-studying.jpg
- Bad: asd98yfbjHYWF.jpg
