I felt so sorry for Ewan McGregor in the Kamino scenes, he looks so uncomfortable on screen, clearly sitting on his own on set, talking to no one.

As for the "dirtying up" of Kamino, I disagree,I think it should be kept as a cold and sterile environment, maybe even made more so. however, I do think it should be the only one in the whole prequel trilogy to be like that, except for the obvious ones like Palpatine's office or whatnot (of course those would be super clean).

ANH and Alien, both out in the late seventies, were the films that really made the whole "used future" concept popular in sci-fi films. And it's really great in both films (and ESB/ROTJ, and the Alien sequels too), it makes the sets feel so real and tangible, live people really live in them. That was a big thing in the OT, and it just flew out the window for the PT. I think it needs to return, especially on Coruscent, which, just by the fact that it's a city planet, should be absolutely filthy apart from the likes of the Senate and the Temple. Same with the other plantets, they should have the used look as well (how about Naboo looks a bit more beat up, apart from the palace of course, it all looks a little too overly idyllic).

And then comes Kamino, which is exactly the "ultra white, clean, perfect future" that SW and Alien subverted in the first place, which would comes as a complete culture shock to the viewer, and perhaps give them a bit of apprehension about the place, which is what you want.

In conclusion to yet another way too long post of mine, I think instead of Kamino getting dirtied up, everywhere else in the PT should be dirited up instead, with Kamino being the unsettling exception.