If you want more favicons than what the fontawesome plugin provide, you can use SVG tiddlers as favicon for your links.
demo: https://telumire.be/TiddlyTweaks/index.html#:[[%24:/ThemeTweaks/svg/style/external_link]]
This will give you something like this (you can of course tweak it) :
![]()
Relevant thread : Trick to convert the core images to SVG image for CSS background
You can also use jpg or png instead of svg, see https://tiddlywiki.com/static/datauri%2520Macro%2520(Examples).html
Let me know if you need help ![]()