The Nightmare of Sigil
Sigil, City of Lost Things, is unique in its population. As any manner of person could end up here, the city is made up of nearly every single race found within the world.
***Check with your DMs before picking a race, for approval and to gather extra information. The following lists are examples, and not the entire population within the city.
These races are populous either because of their large population outside of the city, their social makeups, or their longevity. They're frequently seen as 'ideal' races within the city, with appearances best suited to the city life.
Humans, Elves, Drow are the three primary races
Less common and less ideal than the dominant races, these races can expect little discrimination but otherwise lead normal lives within the city. They find chances of reaching noble class just as easy as any other.
Orc, Half-Orc, Dwarf, Gnome, Goblin, Halfling, Oread, Devil, Teifling, Half-Giant, and Undine are examples of races that get along just fine in the city.
These are races that have an ability to appear humanoid, despite being an entirely different race entirely. As long as their real race is hidden, they can expect positive treatment and to blend in with the common folk.
Dragon, Kitsune, Elan, and Werebeasts are examples of races that when hiding can appear perfectly mundane within the city.
Sigil has a strong prejudice against beast races which goes back generations. Most current dislike of beast races just comes from social norms, but its believed that it started from a perceived understanding that they were beasts first, intelligent races second. They have all opportunities in the city as others, however they will note plenty of obstacles against them.
Tengu, Kenku, Grippli, Kobold, Dragonkin, Foxkin, Ratfolk, Wulfkin, Strix, Nagaji, and Avians are all races that have no reliable way of hiding their appearance, and are unmistakingly beastly.