I somehow ended up with two 'Greetings from' Indonesia cards. Ooops. I don't really mind, though, as they are both lovely - beautiful stamps and gorgeous decorations on the back. ^_^
I had to look up the symbol in the middle as I seem to remember there was initially a picture of a coconut tree there but it was changed. This is what I found, and I think it's pretty cool:
Bhinneka Tunggal Ika is the official national motto of Indonesia. The phrase is Old Javanese translated as "Unity in Diversity". It is inscribed in the Indonesian national symbol, Garuda Pancasila (written on the scroll gripped by the Garuda's claws), and is mentioned specifically in article 36A of the Constitution of Indonesia. The Garuda is a mythical bird and the mount of Lord Vishnu.
It is a quotation from an Old Javanese poem Kakawin Sutasoma, written by Mpu Tantular during the reign of the Majapahit empire sometime in the 14th century, under the reign of King Rājasanagara, also known as Hayam Wuruk. Kakawin contains epic poems written in metres.
This poem is notable as it promotes tolerance between Hindus (especially Shivaites) and Buddhists.
...and the stamps on the second card: