I have a city that is set in a somewhat dusty brown world. Seeing as a lot of you have also modded for Fallout, I was wondering if you could advise me about how to achieve that sort of look.

I think the most important thing here would be your weather. Not only does weather directly set the fog/ambient lighting, it also has an image space modifier. Most of Skyrim's weathers use rather saturated contrasty ones. Make your own ISM that is desaturated and lower contrast. It will make it look more bland and drab. Then set the ambient and fog to your liking and it should look fairly dull and Fallout-y.

Make my own ISM? Wow, I'm starting making my own weather, and I feel a bit out of my depth. Is there a tutorial on this stuff you could point me to? The wiki is rather incompete...
EDIT: Nvm, I accidentally messed with stuff and used the underwater ISM. It makes everything this eery purple that works really well with the atmosphere I'm trying to set up.

Hey, I've gotten a firmer handle on Imagespaces, but even slight adjustments from the normals make these weird ultra bright lighting that I hate. Can anyone suggest values for making a sort of dusty brown drab lighting condition? Also, how would I make the little sandstorm winds that blow around all over fallout?

The sandstorm wind meshes were objects that aren't in Skyrim. However, if you set the lighting properly, you could use the blowing snow objects (Not sure on their exact name) and it would look like sand or dirt.

ISM's are actually really simple, it's just a lot of settings. Each catagory does something to affect vision. I'll go over the super duper basics quickly:

The two checkboxes at the bottom: I'm not sure what display does. Animated means it's an ISM that changes over time, as opposed to one that's always active. You want a non-animated (dont check the box) one for this. Animated ones are for things like fading to black, effects like light blasts (or grenade blast effects from Fallout).

You have your Fade, where you set the RGB of a solid color to fade in over the screen. You also set the strength. A 255/255/255 fade at 255 strength would result in the screen being solid white. Then there's tint, which isn't a solid fade, but rather, well, tints the screen. This could be key in getting the effect you want. Try making it a brownish color (make G and B equal, and R slightly higher to get brownish), with a medium strength (try 100?) That would tint the whole world brown. Mess with this to your liking.

Other settings that may interest you are Saturation, and Contrast. There are two values, I usually just touch the first one. (They are something like a multiplyer and an addition type thing) Try setting the saturation a bit lower, as well as the contrast. That will make the world look more drab.

You shouldn't get super bright lighting for any reason unless you dramatically alter something like the brightness, bloom, or set a white tint of some kind.

Nvm. Figured this out eventually.
The super bright light just seemed to be a factor of having low contrast without adjusted brightness.