Some things wrong with the extension:
- /usr/local/tce.* directories should be root:staff (0:50) with 775 permissions
- system dirs should be owned by root
- the squashfs block size should be 4kb. Our squashfs-tools default to that, upstream currently defaults to 128kb.
- there should be a menu item for an icon to show
As for what causes the icon to not show, if you load another extension with wrong permissions, all extensions after that one will not show icons. It might have been another cause as well, complex interactions with so many extensions.
edit: Attached is the fixed extension.