Here is the result of running the app:

(xfce4-appearance-settings:11582): Gdk-WARNING **: Using Cairo rendering requires the drawable argument to
have a specified colormap. All windows have a colormap,
however, pixmaps only have colormap by default if they
were created with a non-NULL window argument. Otherwise
a colormap must be set on them with gdk_drawable_set_colormap

(xfce4-appearance-settings:11582): Gdk-WARNING **: /build/gtk+2.0-KsZKkB/gtk+2.0-2.24.30/gdk/gdkpixbuf-drawable.c:1257: Depth of the source drawable is 24 where as the visual depth of the colormap passed is 16
The program 'xfce4-appearance-settings' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadValue (integer parameter out of range for operation)'.
  (Details: serial 193 error_code 2 request_code 53 minor_code 0)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)