I wonder what's the reason for the decline in length over the years and why the peak size years seem to be '82-'83.
As an image format alternative, there's avif and webp, but png has the advantage it was in existence during in the lasts BYTE years (1996-1998). "The full specification of PNG was released under the approval of World Wide Web Consortium (W3C) on 1 October 1996, and later as RFC 2083 on 15 January 1997"
The funny thing is, when I search I can't find mention of the GIF/PNG discussions or PNG introduction, while I do find mention of things like WebNFS, OLiVR/VDOLive (wavelet video) and FIF (fractal image format). Perhaps it was out of scope?