[Author Roland Rogers is a 14-year-old 13th Age player whose One Unique Thing is that he Knows All the Monsters. ]
In my opinion, there aren’t enough races in 13th Age that can cause the fun kind of trouble with NPCs in adventuring parties, though the half-orc and the tiefling are good candidates. The possibility of using creatures such as goblins and kobolds as part of your team might cause interesting tensions, and opens a lot of doors for exceptional Backgrounds and One Unique Things.
So here are some optional and very unofficial races for you to consider.
+2 Dex or +2 Int
Bonus Feat: Goblinoids gain a +2 on rolls to filch things.
Filch (Racial Power)
Once per day, you can ‘take 19’ on a roll to steal an inanimate object (money, magic items) off a person, or out of a trap, etc. this means you don’t roll, instead taking a natural roll of 19, meaning you will almost always succeed.
Goblinoids are generally part Human, Halfling or Gnome. Very rarely will Goblinoids be part Elf, Dwarf, or Half-Orc.
Overall, Goblinoids are seen by most as scum, whether fairly or not. It is odd for Goblinoids to be in a group with other races, so the reason you are working in a group could be part of your backgrounds or one unique things.
+2 Str or +2 Con
Bonus Feat: Ogrespawn gain a +2 on rolls to lift things or force things to move.
Fortitude (Racial Power)
Twice per day as a standard action you can heal using a free recovery, but the hit points are temporary hit points, that last until you gain more temporary hit points. (You can use this ability out of battle.)
Adventurer Feat: Add your strength modifier to the temporary hit points. At Champion tier you add twice your Strength modifier; at epic tier: three times your Strength modifier).
Champion Feat: You gain an extra recovery per day.
Epic Feat: You can use this ability three times a day instead of two.
Ogres are not noted for their intelligence, and where they are not fighting, they often work as labourers. Ogrespawn can be more intelligent because they can take after their non-Ogre parent, but they are often expected to do the heavy lifting in adventuring parties.
+2 Dex or +2 Int
Alchemical Knowledge (Racial Power)
Twice per day as a quick action, the Kobold can throw a potion. Roll a D3 on the potion chart below.
1: Poison potion: Level + Dex or Str vs PD – 5 ongoing poison damage.
Level 3: 10 ongoing damage.
Level 5: 15 ongoing damage.
Level 7: 20 ongoing damage.
Level 9: 28 ongoing damage.
2: Flight potion: you can fly for the next 1d3 turns, but you have to land before the end of the final turn.
3: Life draining potion: Level + Dex or Str vs PD – the target is Weakened (save ends) and you heal half of a recovery.
Champion Feat: Once per level, you can, instead of rolling, use a Confusion potion. Make a Level + Dex or Str vs PD – the target is Confused (save ends).
Epic Feat: the Poison potion deals 10 more damage, the flight potion lasts for 1d3 +1 rounds instead of 1d3, and you heal extra hit points equal to triple your Dex modifier when you use the life draining potion.
The kobolds most likely to be found amongst the more numerous PC races are often talented alchemists
Kobolds often work for dragons, or powerful lizardfolk . They are viewed as weaker, or as lower creatures. This might affect how they slot into an adventuring party.
+2 Dex or +2 Con.
Regeneration (Racial Power)
Every round, at the end of your turn, you heal hit points equal to half your Constitution modifier (Champion tier: your Constitution modifier, Epic tier: twice your Constitution modifier). You don’t regenerate when you are below 0 hit points.
On a round when you are hit by an attack that deals acid or fire damage, or if you are Stunned you do not heal.
Adventurer Feat: Heal one more hit point whenever you heal.
Champion Feat: You heal an extra one more hit point whenever you heal.
Trolls are devious tricksters, who also excel in physical combat. Their regeneration ability makes them hard to kill, unless you have acid or fire handy. As a Trollspawn, you are only half troll, which makes your regeneration less potent. You are viewed kindly upon by trolls, who value your intelligence, and welcomed amongst them.
Trollish regeneration has been speculated upon by wizards, sorcerers and the like for many ages. Is it the Trollish flesh, infused with magic? Is it a spell cast on every troll at birth? Or could it be a gift from an Icon, given at the start of the First Age?