The NASA website hosts a large number of images from the Soviet/Russian space agency, and other non-American space agencies. These are not necessarily in the public domain.
The SOHO (ESA & NASA) joint project implies that all materials created by its probe are copyrighted and require permission for commercial non-educational use. [2]
Uploaded a work by NASA image courtesy Norman Kuring, Ocean Color Team. from https://commons.wikimedia.org/wiki/File:Ocean_Color_off_the_Icelandic_Coast_2008-07-10.jpg with UploadWizard