In the thumbnail, the light grey corner is the 'dark' background. You can read dark and light text on it comfortably...
It looks better on Cinnamon than Gnome if you kill that stupid big dark titlebar with my
[/details] metacity-1 - you can adjust size by adjusting the fonts and colour often blends perfectly with the windows;)
Bolimage does a few of the nicer themes... but loves BIG titlebars.
I agree with you that KDE has some elegant theming issues - but Cinnamon's can be better when you get it right... and any theme you find, you simply download (or do 'ocs-install' to your /home/stevebiker/.themes and then sudo nemo and MOVE it to your /usr/share/themes... or copy it and mess around editing what's left in /home).
If you like LIGHTER, then search for Greybird - I liked Greybird-compact, Uploading: thumbnail.png...
NVM - I found an old timeshift - here's a
ZIP for .themes and/or /usr/share/themes