I picked out nypl.org as the site I would analyze.
There are 32 images @1024px full screen size, less if it is under that break point. The total size, of the images, is 1.35MB.
Additionally, there are another 11 svg images, for a total of 43 images. Don’t know how large, but they are single color so I’m guessing 100k for all of them combined. The Lion SVG is pretty complex and has a lot of anchor points.
Thirteen are featured images. So either the most current book choice, featured item with the widest array of appeal and so on.
One is a repeating lion logo, done in svg and then css rules are applied to it to change it’s appearance. This image is used 5 more times as either a smaller home icon or a background element.
The rest of the images are smaller images of less in demand events. Although these seem to be cycled out for featured occasionally.
The website works very well without any images. All the images are properly tagged and the layout does not break or resize by the absence of the images. The layout stays the same.
A site like this loads fast on a 10MB connection or 4glte, but it loads too slow on a 3g connection (as many phone plans throttle to, even with unlimited) or 512kb connections. It loads less (15) images while on a smaller resolution device like a smartphone. A low bandwidth version would be nice for desktop PCs. I think that the images are well spaced and compressed very well for the amount of detail in them.
I just am of the mind that you don’t need a site with a lot of images to effectively find information. Examples are google.com, 4chan, reddit, wikipedia. These are made to be browsed through repeatedly without chewing through a slew of data. I would argue that these can provide as much or more information at a much faster speed. Especially if all you want are dates and times of events or book names without loading a whole bunch of images.