Agreed, the stamps of Papua NG are rich in the culture, flora & fauna of the country, unlike those of some countries which show topics which have nothing to do with the issuing country.
My favourite mammals stamps of Papua, issued in 1971:

30c - Goodfellow's Tree Kangaroo
25c - Western Long-beaked Echidna
5c - Cuscus
10c - Long-fingered Triok (possum)
15c - Feather-tailed Possum