This is related to remote desktop over VNC. I'm not sure if this should be posted in the Desktop or Server section. I'm sure a mod will move this if necessary.
In short, the problem is that CentOS 5 won't recognize PNG files. There are a few errors about it when X starts. The end result is that icons in PNG format don't show up on the desktop or in the menus. I tried re-installing gtk2 and libpng but with no success.
Here are 4 related errors that show when X is started:
/usr/bin/gnome-session: /usr/local/lib/libpng12.so.0: no version information available (required by /usr/lib/libcairo.so.2)
/usr/libexec/gconf-sanity-check-2: /usr/local/lib/libpng12.so.0: no version information available (required by /usr/lib/libcairo.so.2)
** (gnome-session:31286): WARNING **: Failed to load image from '/usr/share/pixmaps/splash/gnome-splash.png': Couldn't recognize the image file format for file '/usr/share/pixmaps/splash/gnome-splash.png'
(eggcups:31356): GdkPixbuf-CRITICAL **: gdk_pixbuf_get_height: assertion `pixbuf != NULL' failed
(gnome-panel:31350): Gtk-WARNING **: Error loading theme icon for stock: Couldn't recognize the image file format for file '/usr/share/icons/Clearlooks/24x24/gtk/gtk-ok.png'