Sjoundi dagur i Paradis

Obtained from umm.is, an information portal about Icelandic artists. They don't specify where they obtained the image. Specific link: http://english.umm.is/UMMenglish/Artists/ArtWork/2058

Published (in black and white) in "Uttenreitter, Poul (1930). Guðmundur Thorsteinsson. København, Henrik Koppels Forlag." work 41. The book has no copyright notice. This may or may not have been the first publication.

Morgunblaðið, November 6, 1958, reports that the artwork was about to be published separately, surely in colour. Perhaps that was the first publication in colour. Morgunblaðið itself also publishes the work in that issue (in black and white).[1]

Note that even photographs which are not artworks have a copyright protection of 50 years from creation in Iceland. Thus it is not clear that this image is in the public domain in Iceland.