I'm not a Northgard insider, just a streamer[www.twitch.tv] who wanted to hype with this. Codes are taken from Northgard Editor CDB file.
So first thing you need to know is most of icons you see like this you can use.
To use a icon you need to surround code with capital letter with square brackets.
Like this [Name].

Down below is a list of most of available icons you can use.

Also you can use these codes in you Steam nickname to be cool like me :P

BASE
[Food]
[Wood]
[Money]
[Building]
[Comfort]
[Happy]
[NotHappy]
[Population]
[Warband]
[Lords]
[SlavePop]
[Lore]
[Faith]
[Wheat]
[Fame]
[Fish]
[Meat]
[Sailors]
[Territory]
[Forge]
[SmithAssist]
[Healing]
[SheepFood]
[Blood]
[Prescience]
[PopReserve]

ADVANCED
[Stone]
[Iron]
[Prestige]
[RimeSteel]
[Gemstone]
[MilitaryXP]
[HuntTrophy]
[GrowthLore]
[MilitaryLore]
[WealthLore]

FALSE RESOURCES
[Levy]
[FaithHappy]
[Nothing]
[LevyHealthBonus]
[LevyAttackBonus]
[LevyDefenceBonus]
[LevyAttackSpeedBonus]

INGREDIENT
[BigGame]
[FreshwaterFish]
[Vegetables]
[Mushrooms]

[GiantFaction]
[Giant]
[GiantCamp]
[KoboldFaction]
[Kobold]
[KoboldFirecamp]
[MyrkalfarFaction]
[Myrkalfar]
[MyrkalfarFirecamp]
[DwarfFaction]
[Dwarf]
[DwarfHouse]
[GayantFaction]
[Gayant]
[GayantCamp]
[MarmennillFaction]
[MarmennillCove]

CIVILIAN UNITS
[Woodcutter]
[Farmer]
[Hunter]
[Fisherman]
[Merchant]
[Sailor]
[InnKeeper]
[Miner]
[Scout]
[Falconer]
[Healer]
[Smith]
[Scholar]
[DwarfChampion]


CIVILIAN VIKINGS
[Villager]
[Slave]
[Seeress]
[Mender]
[Cook]
[Skald]
[RuneMaster]


CIVILIAN CAROLINGIANS
[Peon]
[Woodcutter02]
[Farmer02]
[Hunter02]
[Fisherman02]
[Scout02]
[InnKeeper02]
[Priest]
[Merchant02]
[Sailor02]




MILITARY UNITS

[Warrior]
[ShieldBearer]
[AxeWielder]
[Militia]
[Bodyguard]
[Tracker]
[FieldHealer]
[Einherjar]
[Skirmisher]
[Dragonmen]
[Mercenary]
[MonsterDragonmen]

MILITARY CAROLINGIANS
[PeasantMilitia]
[Lord]
[LordEco]
[LordMilitary]
[Bowman]
[Warrior02]
[ShieldBearer02]
[Sentry]
[Bodyguard02]
[Paladin]


WARCHIEFS
[Hero01]
[Liv]
[Hero02]
[Hero03]
[Hero04]
[Berserker]
[Maiden]
[WarchiefSnake]
[WarchiefDragon]
[HorseHero]
[HorseMaiden]
[Kara]
[KrakenMaiden]
[OxHero]
[LynxHero]
[SquirrelHero]
[RatMaiden]
[EagleHero]
[LionHero]
[Hildegard]
[Carloman]
[Lothaire]
[StoatHero]
[Nominoe]

CAMPAIGN WARCHIEFS
[Berserker03]
[Maiden03]
[Hero06]
[Hero07]
[Hero08]
[NornArmor]
[OxShadow]
[GiantHero]
[GayantHero]
[LichKing]
[Gelon]
[UndeadGiantDragon]
[BerserkerBoar]



FOES
[Death]
[UndeadGiant]
[GiantFire]
[GiantCrow]
[Wolf]
[WhiteWolf]
[SacredWolf]
[SpectralWolf]
[Warg]
[Bear]
[WhiteBear]
[SacredBear]
[SpectralBear]
[BearMaiden]
[SacredRam]
[SpectralRam]
[LynxBrown]
[LynxWhite]
[BabyWyvern]
[Wyvern]




[WyvernUndead]
[Valkyrie]
[SpecterWarrior]
[IceWorm]
[Golem]
[IronGolem]
[IceGolem]
[GiantBoar]
[ColossalBoar]
[Spider]
[RevivedCarcass]
[DummyTarget]
[DwarfKing]
[Fox]




PASSIVE
[Sheep]
[Vedrfolnir]
[WoundedBeast]
[Deer]
[SavageDeer]
[Fish]
[Crow]

Say Hi to me when meeting in lobbies if this was helpful :)
Also you can check out my streams on twitch.tv/voidonscreen if there is any. Peace.