Grzyb wrote on 2023-11-13, 18:59:
I suspect the image I'm looking for came with a graphics card, though - the "640x480x256" suggests some graphics demo, or diagnostics?
Many SVGA cards came with driver disks that included drivers for common DOS applications, and some refresh rate setup and mode test tool. It sounds very likely that this image was presented when you tested whether the 640x480 256 color mode works on your monitor at the currently configured refresh rate.
DOS Days has some info on Orchid graphics cards. I noticed that they made an "improved PGA clone". The prime resolution of the PGA is 640x480x256, which fits perfectly to that image file. This might also explains why we don't see 800x600x16 versions of it, as the PGA only supported this one resolution (and CGA-type resolutions in CGA compatiblity mode).
You might be able to contact Greg Marshall, a designer of the Orchid PGA card (see https://wa-chur-ed.com/looking-back/ ) to ask whether the image was included with the Turbo PGA.
