Those are interesting pictures. You might want to go a couple frames beyond the ones you listed to STS088-724-69 and 70. They're not quite as over exposed as some of the others. Of course the NASA site just describes the object in the pictures as space debris. Personally, I think it looks like a spy satellite - which could explain the lack of a more detailed description. But that's just my opinion based on a quick look.
Its as if photographer has centered object more than background subject. And there are several frames in succession with something in. Seem huge for debris?
Not really. Without knowing how far away the object was when the picture was taken, there's no sure way to know how big it is. So it may not be as big as it looks. Also, space debris could include things like defunct satellites or spent rocket stages that actually are quite large.
You're right about the object being centered in several frames. But that's nothing unusual. The potographer probably saw it, thought it was interesting, and snapped a few pictures.
There's definitely an object there. I would guess they're all the same object, tumbling, but I don't know. (For reference purposes, the images are 65, 66, 67, and 68.) Debris from the Orbiter? Maybe. Debris from something else that happened to pass nearby? Possible; that happens more often than NASA mission controllers would like, and most debris is tracked, so they'd have advance warning and be able to get their cameras out. It's rare for another object to pass close enough to be photographed, but certainly isn't out of the question. Satellite? I'm going to go look up that mission to see if there's anything I can find online about it.
Heh -- reading comprehension fail on my part. The links that I posted include a brief description of interesting features in the pictures, and identifies one of the interesting features as "SPACE DEBRIS". This link will search for all photos identified as pictures of space debris. Since the list is so short, I suspect this is restricted to debris not associated with the mission. So this is likely more than just a paint fleck.
STS-88 was the first assembly mission to the ISS. The crew captured the Zarya module and mated the Unity node to it. They also deployed a couple of small satellites.
These frames were all taken on December 11, 1998, around 20:15 GMT. It was an historic day; the scheduled tasks for the day included the first ingress into the International Space Station. I was not able to find any other reference to these images, but I haven't searched all that hard yet. It's not in the daily press releases, which are heavily focused on the exciting space station work.
One more thought: this could be something which was dropped during the mission. When this picture was taken, they had already completed two spacewalks. Astronauts are careful, but butterfingers can strike anybody. Again, I haven't found any answer to what this is yet, but I'll look later today when I have some more time. ;-) I'm curious now!
I was able to get the links CalliArcale posted to work. But if you're still having trouble, just Google "sts088-724 images" That'll give you what you're looking for.
Let's see if I can post an image successfully.... This is the second frame in the series (STS088-724-66). Shows the object pretty well, though note that as it tumbles in subsequent images, its shape appears to change radically -- so it's a very irregular object. Maybe a thermal blanket or something.