Open Educational Resource repositories listed here cover a wide variety of educational disciplines. They include OERs targeted at lower education levels as well, but advanced search can often be employed to refine results to university-level content.
Europeana – is a gateway to European cultural assets, through through this one site you can search (use the hourglass at top right) in many European national libraries and archives for artworks, cultural items, books, and various archival documents from participating institutions all around Europe. The use permissions are usually clearly marked, though some will require contacting the hosting institution for clarity. Some hosting institutions will not have English translations but pasting the URL into Google Translate may be helpful in such cases. To find an item with the Creative Commons or public domain licensing you prefer -
Although every effort is made to ensure that only reliable, up-to-date OER sites are recommended here, and that the content included by the sites themselves is actually licensed as listed, the responsibility ultimately falls on individual users to ensure that the license (including Creative Commons, Public Domain, and paid for/ individually agreed upon with the rights holders) is correct to the reuser's individual use case. Please make a diligent, good faith effort to ensure the resources you use are validly licensed for your intended uses before you reuse them. Librarians are here to help you, and UNCA general counsel is also available as a professional resource for some questions.