Fotor is hands-down the best free photo editor for Windows 8.  It has a very robust set of features that allows you to modify your pictures by cropping, tinting, etc.  The only thing that it doesn't have is a red-eye function.  But a new version is coming soon!

The best part is that it's all free.  And for non-Windows 8 users, it has a desktop version that runs on Windows 7 or 8. So if you like a traditional Windows interface (not that much different from the Windows 8 one), download the desktop version from the manufacturer's web site at www.fotor.com.