This is 'Mahou Sensou' theme. This theme can be installed on windows 8 and 8.1. Mahou Sensou itself tell about Nanase takeshi, a normal student which turn to be a magician by Aiba Mui. An unknown magician that collapsed on  the ground campus. 

For the download link scroll down this page!

Screenshots:

Download Windows 8 theme | download tema windows 8 | windows 8 tema | windows 8 | windows 8.1 | Mahou Sensou | Magical warfare | 魔法戦争