For those who want the reverse—a retro look—this tool is available on GitHub to bring classic elements back to newer systems. Where to Download Free Themes
A community-driven site with easy-to-install theme files. Performance Tip: Optimize Visual Styles best windows 10 themes free download for windows 7
A specialized dark theme that replicates the "Dark Mode" found in later Windows 10 updates. For those who want the reverse—a retro look—this
A refined version that blends Windows 10’s flat colors with the smooth animations of Windows 7. A refined version that blends Windows 10’s flat
Windows 10 Themes for Win 7 Final by sagorpirbd on DeviantArt
If you want more than just a background and color change, transformation packs modify system files to change the Login Screen, Start Menu, and System Icons.
These "Visual Styles" provide the closest look to Windows 10 while staying within the Windows 7 environment.