I try to save most things on Pintrest, because it allows saving pictures with a direct link to the source.

You can search the Swedish museum archives by graves: Birka chamber graves or by a specific criteria: search on Historiska.se.

Sweden: Nordiska Museet

National Museum

Iceland:

One way of searching for Norwegian finds is this site: Universitetsmuseum, or search for pictures with a keyword here: Fotoportalen, Unimus.no.

Academia.edu is a great source of articles.

Museums with digitalised archives:

Poland:

Koszalin Museum

Śląsk Opolski Muzeum

Great Britain:
British Museum

Victoria and Albert Museum

France

www.rmngp.fr

[this page will be constantly changed, as new sources will be added]