I'm not having a lot of luck with this. In the old RSS method, you could search for "IMG-20151203-WA0020" which would mean WhatsApp picture #20 from 2015 / December / 03. You would get a big list of stuff, and then you could always increment it to WA0021 or change the date and start over, and get plenty of results.
However, if you search like this on google.com: site:picasaweb.google.com IMG-20160501-wa00010 you'll get just a few images, and often days you'll get absolutely nothing, which seems unlikely as all my searching via the RSS method, never once did I get a day that not a single image was posted. What am I doing wrong?