There are 2 repositories under plasma-theme topic.
Materia KDE customization
A modern style for qt applications.
A Dark theme for both KDE and GTK based DEs, deeply inspired by the Ayu Dark color palette
Clean, Flat, Δ Theme for Plasma Desktop
A new modern, essential and timeless approach to your desktop.
My plasma customizations.
Monochrome theme for KDE Plasma.
Minimal glassy theme for KDE plasma
Roxo for KDE plasma.