So far I've only found two broken articles
DTMF Tones, Fourier Transforms, and Spectral Analysis
and
Ahoy-hoy!
among the 290 that I have written. I believe I've fixed both of them.
These two related articles were written about the same time, February and March of 2014. The embed HTML in both articles that references photographs uses the iframe HTML tag. Articles in my blog written before and after that reference photographs do not use iframe, and seem to render okay.
Some judicious web searching led me to some discussions amongst Flickr users as to the iframe embed code no longer being supported by Flickr. My current thinking is that that at some point Blogger generated the iframe HTML tag to embed images, and Flickr eventually declined to support it.
Thanks, Cloud.
If you come across an article in my blog that has a big block of white space where you think an image ought to be, please comment on that article and I'll do my best to fix it.