Errata: Magenta is the transparency color, not purpole. This was a typo.

Max bitmap size is 24x24. If you used 8-bit, itshould work. I tried it myself on 2 units. You probably did not use a conventional software to make it and it used a different color map?

Please, send me a link to your 24x24 8-bit bitmap. I will have a look at it.