Not sure what pieces these are. The piece in the back of the photo has a large red X painted on the surface. All major wreckage pieces had a red X, and I'm told this is done to mark the wreck site as a known crash, as to not mistake the site for a recent disaster.  The section with the yellow paint is possibly part of the rear fuselage just in front of the vertical stabalizer. I'm not a B-17 expert so if anyone knows better just holler.