In this first photo, there is a small brownish-grey object, clearly-defined against the sky in the background, located below the triangle-shaped plume that is emanating from the solid rocket booster. It is just below the point where the fiery plume turns into grey-colored smoke. If you zoom into this part of the photo and enhance the resolution, it appears that this object has a nose of some sort that is pointed up and slightly to the right. The size of this object, in proportion to the size of the rocket booster, would appear to be consistent with the size of the Challenger's crew cabin. The position of the object is also consistent with where the crew cabin would be in relation to the main explosion after it had separated from the rest of the shuttle.
There is clearly a cylindrical-shaped object in this photo, directly underneath the two smaller plumes at the top. Based on what I've read about the disaster, this may be a large piece of wreckage that was later recovered from the ocean floor -- a section of the main body of the shuttle between the tail and the crew cabin.
This third photo contains two distinct objects. I cannot refine the resolution of this photo enough to distinguish what exactly the object is near the bottom right corner, but it is clearly something solid from the shuttle that was not engulfed in the main explosion. There is also a long, cylindrical object in the center of the photo (between the two closely-spaced contrails) that appears to be the main booster rocket.
