Here's a list of Hetalia characters that are left so far. If the names are crossed, it means they're taken. I'll reserve them for you if you wish.

North Italy
Germany - Huntress Kitteh
Japan - elojello10
America - Princess Mint the Great
Canada - XxThe Graceful AssassinxX
England
France
China - XxThe Graceful AssassinxX
Russia - Russian Vodka Winter
Spain - Kitty the Ninja Pikachu
South Italy - Ocean Ecco
Hungary
Austria - Russian Vodka Winter
Prussia - Gil Beilscmidt
Poland
Lithuania
Latvia - Porkcow001
Estonia - Kitty the Ninja Pikachu
Belarus
Ukraine
Switzerland
Liechtenstein - animekittyninja-aka kiki
Sweden - Kitty the Ninja Pikachu
Finland
Iceland
Denmark - xXOtaku_HunterXx
Norway - Dionnysia
Turkey
Greece
Egypt - Russian Vodka Winter
Cuba - Deceptive Prince Luthor
Taiwan - RespectfulRose
South Korea - GamerSurfer
Hong Kong
Vietnam - dragon_fire_313
Thailand
Seychelles
Sealand
Wy
Seborga
Netherlands - RespectfulRose
Belgium - Dionnysia
Monaco - icuteie
Bulgaria - Ryuna the Guardian
Australia
New Zealand
Romania - dragon_fire_313
Cameroon
Kugelmugel
Molossia
Cyprus
Turkish Republic of Northern Cyprus
Hutt River
Ladonia
Macau
Osaka
Picardy
India - boo133
Tibet - Ocean Ecco
Portugal
Rome - Kitty the Ninja Pikachu
Germania - Porkcow001

(If I'm missing any, let me know.)