Now I have added some stamps from other continents.
America
Confederation Argentina, Barbuda (British colony), Bogota, British Columbia, British Virgin Islands, British Honduras, Carupano. Corrientes, Baja California, Dominica (British colony), Venezuela Departmentos del Sur (Peru), Confederated states of America, Imperio Mexicano, Galapagos, Montserrat, Mustique, Nevis (British colony), Prince Edward Island, Saint Christopher (British colony) and Tobago (British colony)

Europe
Kosovo, Crete (Greece administration), Kurland, Lübeck (German state), Maribor (Slovenia), Kransko (Austria), Modena (government of Sardinia), Multan county (ottoman empire), Mytilene (Greece), Territories of Neapol, Parma (Italia), Port Lagos, Poznan (Poland), Pristine, Pleskow, Rethymno, Romagna, Romania (German occupation), Romania (Astria occupation), Northern Ingria, Southern Italia (allied postage), Shkodra (Albania), Salonika (Russian postage), Srem-Baransko territory (Serbia), Thesalia (Ottoman empire), Vienna and Southern Austria, Zante (German occupation)

Europe
West Thrace (ottoman empire)
Australia
British New Guinea, Gilbert Islands (British colony), Marianas Islands, Samoa (Kingdom)- 3 times, Samoa (New Zealand occupation of German Samoa), Samoa (New Zealand mandate territory), Tahiti, Tuvalu and Micronesia

Asia
Abchazia (Russia), Alwar (Indian state), Anatolia (Ottoman empire), Bamra (Indian state), Bandoen (Java), Bangkok, Bussahir (Indian native state), Beyrouth (Russian post office), Bushire (British occupation), Central Plains (liberated area), Chiba (Japan), Duttia (Indian state), Dhar (Indian state), Gurkha kingdom (Indian state), Jammu (Jammu and Kashmire), Japan (British occupation), Jasdan (Indian state), Java (Ned. India), Java (Japanese occupation), Jerusalem (Provisional government), South Korea (US occupation), johor (Malaysia), Johore (Malaya - british occupation), Johore (British protectorate), Johore (Japanese occupation), Kashmir, Cilicie (Turkish administration), Kudonion (Greek occupation), Kuwait (British administration), Kuwait (Indian administration), Malaysia

Asia
Naxcivan (Azerbaijan), Mountainous Karabakh (Azerbaijan), Orcha (Indian state), Peshavar (Indian state), Priamur region (White government), Soruth (Indian state), Shahpura (Indian state), Central China (Japanese occupation) - whole line, Tibet, Syria (French mandate territory) and Timor Leste

This is just piece of collecting WW. I still miss some. Hope that it was at least a little bit interesting for you.