Below is a video of this work in action. In the video, you can see the RPi, decoding the Blender foundations Big Buck Bunny in 720p resolution and outputting through HDMI to a monitor.
To recreate the video, use this rpi_demo_defconfig then run the following on the RPi. The rpi_demo_defconfig enables buildroot to build gst-omx.
# wget http://blender-mirror.kino3d.org/peach/bigbuckbunny_movies/big_buck_bunny_720p_h264.mov
# gst-launch-1.0 filesrc location=/path/to/video ! qtdemux ! h264parse ! omxh264dec ! eglglessink