Sasaki Ganryû — From the series Biographies of Our Country's Swordsmen (Honchô kendô ryakuden). Woodblock print (nishiki-e).
Photo Credit: By Utagawa Kuniyoshi (Japanese, 1797–1861) - Museum of Fine Arts Boston - https://web.archive.org/web/20210516084701/https://collections.mfa.org/objects/213420, Public Domain, https://commons.wikimedia.org/w/index.php?curid=105363807

Algernon Charles Swinburne in 1865 — By London Stereoscopic & Photographic Company - National Portrait Gallery: http://www.npg.org.uk/collections/search/portrait/mw113995/Algernon-Charles-Swinburne?LinkID=mp04389&search=sas&sText=Algernon+Charles+Swinburne&role=sit&rNo=10
Photo Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=26673205

How many Triangles - solution —
Photo Credit: unknown

CincinnatiPublic Library 1874 —
Photo Credit: unknown

The Hero's Journey - Joseph Campbell —
Photo Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=10284342

Full Moon — Photo by Rachel Moore on Unsplash
Photo Credit: Rachel Koore

Glasses, notes on book — Photo by Kevin Canlas on Unsplash
Photo Credit: Kevin Canlas

Title page of Newton's Opticks (1st edition) —
Photo Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=510265

MySQL Creators — David Axmark (left) and Michael "Monty" Widenius, founders of MySQL AB, in 2003
Photo Credit: By Werner Popken - photo taken with Panasonic FZ1 on a conference, available light, by Werner Popken, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=405275

MySQL logo —
Photo Credit: https://labs.mysql.com/common/logos/mysql-logo.svg, Fair use, https://en.wikipedia.org/w/index.php?curid=67634535

Michael ”Monty” Widenius — Shot during MariaDB’s Developers Unconference 2019 in at Hudson River Trading, New York City
Photo Credit: By SofiaEk - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=77113180