I have a number of blocks that are inserted on two different layers. In the tool palette the same block is on two different palettes with different labels and layers. Only one will show an image. I can update the image for the one that doesn't work and exit AutoCAD, but when I come back in it has reverted to the blank white box.
.ATC file for the one that doesn't work
<Images option="0"><Image cx="32" cy="32"/><Image cx="64" cy="64"/></Images>
ATC file for the one that does work:
<Images option="0"><Image cx="32" cy="32" src=".\Images\Block tool_E7635736-FFBC-4BC6-85D9-FFF57A7E8E2C.PNG"/><Image cx="64" cy="64" src=".\Images\Block tool_E7635736-FFBC-4BC6-85D9-FFF57A7E8E2C_2.PNG"/></Images>
Also this is an example where the image name should be SPOT-ELV32.PNG not Block tool_E7635736-FFBC-4BC6-85D9-FFF57A7E8E2C.PNG. About 1/3 of my images use the long name format instead of <blockname>32.PNG or <blockname>64.PNG