These are user-created themes which were made publicly available:

Midnight 👤 tobealive	EOTE 👤 tobealive
Trilium Themes 👤 Abourass	MaterialDark 👤 ZMonk91
lightslategray 👤 jaroet	melon-4 👤 raphwriter
Neon_Dark 👤 Engr-AllanG	Coder_Dark 👤 Engr-AllanG
velvet 👤 idelem	Dark Plus 👤 SADAVA
Solarized 👤 WKSu	Nord 👤 en3r0
Bear Note Light 👤 AllanZyne	Bear Note Dark 👤 AllanZyne
Miku Hatsune 👤 Sebiann	Midnight 👤 cwilliams5
Blue (light) 👤 SiriusXT	Blue (dark) 👤 SiriusXT

If you would like to add your theme to this gallery, write a new post in 👐 Show and tell.