I took the default Cinnamon Theme from Mint and made a few changes. I think the theme was good as it was, but I wanted it to be slightly more minimal.

Changes:
Removed excess borders and inset shadows
Squared up the corners to a radius of 1px.
Adjusted the contrast of the Window list and removed borders/inset shadows for a cleaner look. Adjusted Hover and Active window contrast.
Adjusted the contrast of the menuitems hover and removed borders/inset shadows for a cleaner look.