Golarion is a diverse world with more than 50 races. Some of them are extremly common and part of almost every community, others do not exist as far as the common person knows. Here you will find guidance what races work well in this campaign and how we would balance races of different power levels.
Races beyond the core races are uncommon in Korvosa and its surrounding countryside. While there could always be a reason for a member of those races to be in Korvosa - it's a port city after all - you have to weave this reason into your background story.
Some races are also more powerful than others, at least at lower levels. Rather than non allowing those, they will be adjusted via the number of traits your character is getting at level 1. Below you will find all races of the pathfinder core rule books assigned to tiers - a concept I am borrowing from Alex Augunas's blog - and different tiers will get a different numbers of traits:
Races in tier 1 will get 3 traits, those in tier 2 will get the standard 2 traits and those in tier 3 will get 1 trait.
Tierless races are not available without GM consideration. Specifically, this usually means that you need a REALLY good backstory to explain why your character is in the campaign. For evil races, this backstory needs to include a description of why your character can or will work with the people in the party—I don’t want irreconcilable infighting between players at the table. If I allow your character, the race’s effective tier is noted next to its name (1 for Tier 1, 2 for Tier 2, and so on). Races on the Tierless List with a 0 next to their name will never be permitted as a PC, so don’t bother writing the character.
Tier 1:
Catfolk, Changeling, Dhampir (Inner Sea Races only), Dwarf, Elf, Gillman, Grippli, Gnome, Half-Elf, Half-Orc, Halfling, Human (except Azlanti), Ifrit, Kitsune, Nagaji, Oread, Ratfolk, Samsaran, Sylph, Tengu, Undine, Vanara, Wayang
Tier 2:
Aasimar (Inner Sea Races only), Aquatic Elves, Fetchlings, Lashunta, Skinwalker (Inner Sea Races only), Suli, Tiefling (Inner Sea Races only), Vishkanya
Tier 3:
Gathlain, Ghoran, Wyrwood, Wyvaran
Tierless:
Alien (0), Androids (0), Drow (3), Deurgar (3), Goblin (1), Hobgoblin (2), Human (Azlanti) (0), Kasatha (3), Kobold (1), Merfolk (0), Monkey Goblin (1), Noble Drow (0), Orc (2), Svirfneblin (3), Strix (3), Syrinex (3), Triaxian (1), Trox (0)