First Impression: sorry for the score, your worst between your best and your third best, a bit surprising
Composition: Not sure about the angle of the shot
Subject: correct, but, as yanko says, you surely knew you were on risk. IMO meets the challenge.
Technical: it seems not very sharp to me, even a bit blurred... The colors need more punch
Improvement: IMO many room to improve here (pun not intented...): colors, angle of shot, focus
Summary: don't worry for this score, you're achieving very good scores.
Well it looks like you got hammered here pretty good. For starters, that's a room as far as I can tell even though it's outside. You couldn't tell with a lot of the images if the room was indeed empty or if it was indeed a room period yet many did well including taking a ribbon so I don't get the DNMC votes frankly.
However, you probably knew this was a bit of a risk going in so I think you needed to really give the voters that something extra to tell them why you are entering this shot and you didn't do that. The bone just seems like it was tossed there and you shot it. I do like how the wall curves around and frames the bone but beyond that I don't really see the appeal of this scene you captured. If that wall was indeed left by the vikings maybe you should have shot a viking helmet instead of a bone? Sorry I am not more helpful than that! :)
Cute idea but I think you're going to get hammered for going outside the box - in this case a room. I have a feeling this is a room in an ancient ruined house? If it is, you've met the challenge but nobody knows that because it just looks like a corner of your garden