As of 4.2.0, the notes plugin no longer uses any user-specified icon. The default is supplied instead. And while we're on the topic, is it possible (in future versions) to have the notes plugin use an icon from the GTK theme?
Created attachment 187 Patch for the notes_applet.c file
Ups... this is the comment for the above attachment: I think that somebody forget the line gtk_widget_destroy(widget); in the implementation of the void notes_destroy_cb(GtkWidget *widget, NoteApplet *notes) function. I make a patch (diff -u) for the notes_applet.c file.
Also yours, duno if it's still valid since quite some code has changed.
I will close this bug. For the moment I don't/won't support customized icon.