Embedded shadow (cburnett v1, I believe) pieces for lichess.org, chess.com, chessable.com and listudy.org.
lichess example: https://i.imgur.com/6YrQbDb.png
Chessable example: https://i.imgur.com/8pfBtg6.png
Firefox NOTE: This doesn't work reliably on lichess and Tampermonkey using the default settings. To fix it, you need the recent version of Tampermonkey and to have settings in advanced mode. Near the bottom, under "experimental" enable "Add Tampermonkey to the HTML's CSP". Should work in Violentmonkey by default. Other userscript addons for Firefox not currently tested.
CREDIT: Based on this style for Lichess: https://userstyles.org/styles/185735/lichess-pieces-with-shadow-base64-encoded
WARNING: That site is probably one of the worst in the internet. Visit at your own peril.