If your original image is under 1MB, this handy tool: Make a Thumbnail, will create a small image (from 100x100 pixels to 300x300 pixels). You can then link this on the website to a larger image or just use the small thumbnail as a button to go to another section of the site.
Very easy to use. Just click browse to locate the image on your computer, select the size desired, and click "Make a Thumbnail"
Example to the left of gazing out the window on a lovely fall day. The 100x100 pixel image is only 4k!