Hi Gijoe!
I'm happy if I help
Unfortunately only copy module_icon.png to xoops_root_path/modules don't work.
The properties of image show '..../module_icon.php
I re-name module_icon.png to module_icon.php [ ] and the gif is ok.
But this maybe cause mal-function in module, I don't know. The rename op. is a little bizarre to me [and I try and test this! ].
All the best
Joao Barroca
aka
beduino