its probably a mosaic they put together.
From the lower part of that image, which consists of not-as-sharp detail, I'd say that's right. Formed of whatever highest-res monochrome images they have (from various distances and angles, stretched and skewed to match the eventual viewing angle) and hue-washed with the lower-res colour photography.
(In the later images on that page they've left dark spaces where they don't have tiling information, instead.)
You might well find higher-res images of a subset (in fact, you do, already, that page just brought my (slow) internet to a grinding halt while revisiting it to check what I'd noted the first time round), or they might be able to improve the image over the next few months as more and more of the stored data is trickled back to Earth for analysis and the-making-of-prettier-pictures as all the information gets added back in. But the smudges will probably end up being more obvious.
Still, it's pure (dwarf-)planetary pr0n! I covered my walls with Mandelbrot Set posters when I was at university, but these days I'd probably consider that too clichéd (moreso than it probably already was, back then) and instead snap up this kind of thing. (I've had a deep-field starscape poster above my bed right now, but it has had to compete with a lot of Escher and Discworld-themed prints, decoration-wise, for more than a decade, now, so I'd hardly say its a current trend.)