This gorgeous Valentine card from around 1860 has lacy, beautifully detailed, cut-and-embossed paper making it up. Unfortunately, it uses text speech ("U.R. kind"), so it's clearly going to kill the English language within 170 years or so.

This 1880s Valentine card is apparently for soldiers. "Home from the war. I pray you smile on me."

This one's by Victorian artist Kate Greenaway, better known for her children's book illustrations.

Vernon and Irene Castle spent a career dancing together.

Two Lovers Beneath an Umbrella in the Snow by Suzuki Harunobu

A couple at the 2021 NYC Pride March

The Stolen Kiss by Jean-Honoré Fragonard

"Love or Duty" by Gabrielé Castagnola

A lesbian couple by Hartknut. Simmer

Love can also be tragic: in Echo and Narcissus by John William Waterhouse, we see Echo, who loves Narcissus, and Narcissus, who loves himself. It doesn't end well for either.