The developer preview of Android L has already been released for select devices, but, alas, only a small percentage of Android users will be able to tinker with it yet. Fortunately, the rest can also experience the new Material Design to some extent by flashing the Android L keyboard on their devices, courtesy of XDA.
Still, there are certain prerequisites – you'll need a rooted device that is running Android 4.4 KitKat or higher with a custom recovery on board (either ClockworkMod or TWRP will do the trick). You'll also need to uninstall your stock Google Keyboard. If these conditions have been met, you can simply flash the Android L keyboard via the custom recovery. In order to get the Material Design look, you should head into the settings menu of the newly-installed keyboard and change the color scheme.
The app has been successfully tested on some of the more popular Android devices, most notably the Nexus line, the Galaxy S III, S4, S5, the HTC One (M8), the LG G2, so if you are sporting one of these, you shouldn't have any issues. Of course, you'll need to strictly follow the instructions - these, along with the Android L keyboard itself, can be found at the source link below.
The new Android L wallpapers and its boot animation have also been extracted - once again, thanks to the XDA folks.
Android L keyboard
source: XDA via AndroidGuys