Wikimedia Commons is an online repository of free-use images, sound, and other media files. It is a project of the Wikimedia Foundation — the organisation behind Wikipedia. As regards to digitisations of public domain images found on their site, their official position is that "faithful reproductions of two-dimensional public domain works of art are public domain, and that claims to the contrary represent an assault on the very concept of a public domain". This means that you will find on their site digitised works under a public domain license regardless of whether or not the original digitising institution has claimed copyright or restrictions on use. (Wikipedia)