I have updated the PlayOnLinux software to 4.1.8 version. Before this, I had all my programs with custom icons in the Unity Launcher bar, but now I must set them again. For example, with Notepad++ I have created a file called
~/.local/share/applications/Notepad++.desktop
with this content
"
[Desktop Entry]
Encoding=UTF-8
Name=Notepad++
Comment=PlayOnLinux
Type=Application
Exec=/usr/share/playonlinux/playonlinux --run "Notepad++" %F
Icon=/home/ignacio/Pictures/Icons/Notepad++.png
Name[fr_FR]=Notepad++
"
And the Icon path is the Notepad++ icon symbol.
However, with this the icon change occurs in nautilus only, and the Unity launcher bar icon is not changed. I don't know what else was necessary to do.
Cheers and thanks for anything,
Ignacio