Re: any restrictions/rules for kids' clothing?
Mine are 18 months and 3 year old girls. Restrictions include: no baby bikinis (they just ick me out), try to avoid super short shorts and tightly fitted jeans (the 2nd for comfort reasons, I usually buy boys jeans). Generally no halter tops unless there is another shirt underneath, wear a pair of shorts under dresses. I also hate character stuff, so none of their clothes has disney princess or dora or tinker bell or anything on it, though we do have a pair of Lightning McQueen Slippers (DD1 is crazy about cars in general), and a few hand me down Winney the Pooh things. Nothing that floofs around the chest and gives the illusions of 'breasts'.
Since they are younger, and DD1 picks out her own clothes, her outfits don't always match. My personal favorite was a bright orange shirt, bright pink shorts, blue sandals, with her winter hat and mittens. :P
I'm sure as they get older we will have other rules. My parents were pretty laid back about clothes, and I made reasonably good choices.