In addition, you can now right-click any directory and change its color (credits to Marco Alvarez Costales and the Elementary project for original work and ideas). That's quite handy to quickly recognize your favorite places in a long list of directories.
The default MDM theme for the login screen now features a slideshow. Additional HTML themes were also installed by default, including some of the great retro-looking themes from Sam Riggs, a new modern theme from Philipp Miller and some flat themes from Bernard.
Finally, there are backgrounds galore in Linux Mint 17.1. All the backgrounds since the previous LTS (Maya, Nadia, Olivia, Petra, Qiana) were added, as well as a nostalgic selection of the best backgrounds from the early days of Linux Mint. You'll even find the notorious Dew background from Linux Mint 7 Gloria in there