This image is from the British Library archive, a book called The Cruise of the Marchesa … With maps and … woodcuts drawn by J. Keulemans, C. Whymper and others. by Francis H. H. Guillemard, a medical doctor who decided to explore New Guinea (and the Malay Archipelago) rather than settling down in Kent to practice medicine. Then, Cyprus. Then, Morocco. Then, Cambridge, where he became geographical editor of the Cambridge University Press.
The book says this about the korowaar:
One article of furniture there is which is found in every room – the korowaar, a carved wooden image a foot or so in height, the hands generally represented as resting on a shield, which, like many of the Papuan carvings, is often of very good design. These are not idols, as they have been represented to be by some travellers, but the media by which the living hold communication with, and are kept in memory of, the dead. If any individual die a korowaar is immediately constructed, for unprovided with an earthly habitation his spirit could not rest. On the commencement of the carving a feast is held, and as each portion of the image is completed a dance commemorates the occasion. When finished the image is either placed on the grave or carried to the home of the nearest relation, where it is treated with great respect.