Guilty as charged... I have had a play round with the image and have probably overcooked it, but time is short and re-shooting it is not an option for this challenge. Thanks for the comments. - Steve
Interesting shapes and composition, but it comes across as flat because it's just too...gray. Try increasing contrast and then maybe adding some sharpness. I suspect you used flash because it is in such a dark location, but the flash has also flattened the image. If this is near your home, you might try to go back when the sun is at a better angle. Or, you could use a tripod and slow shutter speed in order to use only natural light.
--Mary Anne