I have a .desktop file for a Wine application. It works as expected but unity shows the default icon instead the correct one. Of course I have several of them in their respective /home/$USER/.local/share/icons/hicolor/... folders.

Maybe problems with icon cache? I've tried gtk-update-icon-cache but nothing changes. Also unity --reset and unity --reset-icons. These two last commands in a separate TTY and I had to CTRL+Z both of them.