My List.xml file
<ImageItem Image="TFTP:Desktops/320x212x12/thumbnail1.png" URL="TFTP:Desktops/320x212x12/image1.png"/>
</CiscoIPPhoneImageList>
If the background does not change it usually means that the file does not have the EXACT dimensions as required by the manual. I believe that for an A thumbnail would be required to have a selection be present in the selection screen. Looking at the provided XML scraps, I reckon you would have to switch the URL of the thumbnail and the Image as they appear to “the wrong way round”.
Found and fixed the problem. List.xml file needs to be in TFTP:Desktops/320x212x12/ folder. I previously put it under the root tftp folder. Sad things is no instructions mentioned about this.
I’ll tell you what though, I bet it felt really good when you finally had it working, huh?
Congrats on figuring it out.