Platinums may get upgraded to a preferred room in the category booked - a very subtle upgrade that you may not notice unless you know the property well. Platinums should not really expect any significant upgrade.
Diamonds are supposed to get a complimentary upgrade to the best available non-suite room. Some properties do not always do this and others routinely go above and beyond when circumstances allow. Suites maybe confirmed using a DSU if inventory is available but properties are not required to provide them without these instruments - although a few properties do routinely. You're supposed to get club access if there's a club or a restaurant breakfast if there is no club or its closed.
Courtesy Card holders (unpublished level that is by invitation only - formerly property owners and other invited individuals - presently appears to be high spenders - think $25,000+ annually) are supposed to get upgraded to suites (even presidentials) when available at check in.