I have installed Thunar 0.8.0 and Image Thumbnails are not displayed. Thunar is compiled without gnome thumbnailers enabled.

gdk-pixbuf-query-loaders shows support for png and other image file formats.

Here is the output of ldd /usr/lib/gtk-2.0/2.10.0/loaders/libpixbufloader-png.so:

linux-gate.so.1 =>  (0xffffe000)
libpng12.so.0 => /usr/X11R6/lib/libpng12.so.0 (0xb7edd000)
libz.so.1 => /usr/X11R6/lib/libz.so.1 (0xb7ec9000)
libgdk_pixbuf-2.0.so.0 => /usr/X11R6/lib/libgdk_pixbuf-2.0.so.0 (0xb7eb3000)
libgmodule-2.0.so.0 => /usr/X11R6/lib/libgmodule-2.0.so.0 (0xb7eb0000)
libdl.so.2 => /lib/libdl.so.2 (0xb7eab000)
libgobject-2.0.so.0 => /usr/X11R6/lib/libgobject-2.0.so.0 (0xb7e72000)
libglib-2.0.so.0 => /usr/X11R6/lib/libglib-2.0.so.0 (0xb7ddf000)
libm.so.6 => /lib/libm.so.6 (0xb7db8000)
libc.so.6 => /lib/libc.so.6 (0xb7c75000)
/lib/ld-linux.so.2 (0x80000000)

Best Regards
Marcus