"Where do the background images on this website come from?"
Neil is an avid mountain biker. These images come from some of his rides as well as a series of publicly-available webcams strategically placed around the San Francisco Bay Area by government entities, utilities, and private individuals.
He's assembled many of these live webcams at the website trailcams.fun so that hikers and bikers know if any area has fog or clouds, before they choose where to go for the day. Surprisingly, it can be clear, sunny and warm in one place and cold, foggy and cloudy just 10 miles away. Microclimates.