Show Warnings when GTK Resources are not loaded
Currently, the way to "debug" these sources of failure is described as such in the documentation:
If you need to detect failures to load the file, use gdk_pixbuf_new_from_file() to load the file yourself, then create the GtkImage from the pixbuf.
It would be nice, if, when we try to load a resource from an XML file, a warning is produced either at runtime or build-time, when a resource is not found too.