@Crutch
I focused on TIFF because it is more compatible with old and new Macs than even GIF or JPG. MacPaint is best for old Macs, but modern Photoshop doesn't like it. Hence my use of TIFF (no layers, no compression -- just the basics).
I spent a lot of time on the HyperCard solution, so I will likely go with that. But I wish there was a script command for HyperCard v2.3 that could hide the cursor (pointer). I can mostly slide it into a corner, but a few pixels still display.
I got Photoshop v1.1 to work after a fresh install, but again, I probably will use HyperCard this time. Photoshop v1.1 surprised me because not only can it display the images full screen without a menubar, but it can open the TIFF files created on an M1 Mac under MacOS Monterey too. Pretty slick!
On FaceBook, Nathan Andrews mentioned this to me...
TIFFWindow is a shareware XCMD that displays TIFF imagefiles in a window under Hypercard. It understands 1, 2, 4, 8,and 24-bit images, as well as compression....
archive.org
But it seems to display TIFF images in a window, rather than full screen, which isn't what I want. However, if HyperCard v2.3 could import TIFF files created by modern Macs directly, without my having to open them in Canvas and resave them first, that would be a time saver. But in the future, I probably will just use Photoshop v1.1 because that can open the files directly and do what I want.