Sounds similar to an EGA setup.

At any rate, BECAUSE your capabilities are limited, you should keep it simple and professional looking. Putting in horrible graphics just because the system is "kind of" capable of it, isn't a particularly good reason to do so.

Zoom is a fairly good example of KISS, but I still think that even with those limitations they could all look more modern. Assuming the fonts are not required to be built-in to these devices for those screens, font choice is key, followed by a simple graphic design that doesn't TRY to be bright, vibrant or snazzy. Hide the system's limitations, don't advertise them.

Incidentally, why are these machines still stuck in the 1990's...