The station can accomodate 3 crew in the downscaled configuration.
2 staterooms that were to be temporary are located in the Russian service module Zvezda. I *believe* a third stateroom that fits in an equipment rack space has been delivered to the station. If not, the third occupant is still making do in the Destiny Lab without a "real" stateroom. At least Destiny has a really nice window.
All these were supposed to be temporary measures to provide minimual privacy until the now-cancelled habitation module could be launched. The hab module would have allowed room for 7, and was mostly assembled. The module has been reallocated to ground based research.
Another option was presented to NASA for a more roomy approach. The Boeing-built hab module was another aluminum can, pretty much the same dimensions as the other modules.
Enter TransHab. Transhab was a design that was the same dimensions as the average ISS module when launched...
On orbit, the module would be inflated to triple the diameter, providing much more room.
Nasa scrapped TransHab after 2 test articles had been built ans showed promising results.
TransHab has however had new life breathed into it. The design being used by Bigelow Aerospace for their Genesis, Sundancer, and BA 330 modules are direct desendants of Transhab.
AG