This is one of the first games created to look like a painting. The art was inspired by impressionistic painters, particularly Cezanne.
The "Ballad of the Goddess", which is played several times by Zelda on her harp, is, in fact, "Zelda's Lullaby" from The Legend of Zelda: Ocarina of Time (1998), but then played in reverse.
This is the first Zelda game with a fully orchestrated soundtrack. For Zeruda no densetsu Towairaito purinsesu (2006), composer Koji Kondo had recorded an orchestral piece that played during the intro sequence after the title screen, but for the rest of the game, his superiors wanted traditional synthesized music, as orchestral music was felt to not be "gamey" enough. After composer Mahito Yokota had convinced Nintendo to use an orchestral soundtrack for Super Mario Galaxy (2007), he and Kondo made sure that the Zelda series would follow suit.
It is mentioned to Link in the beginning of the game that this year is the 25th anniversary of the Sky Ceremony. This is in reference to the 25th anniversary of The Legend of Zelda game franchise.
In terms of the Legend of Zelda time-line, "Skyward Sword" is considered the first game and takes place centuries before the events of "The Minsh Cap," "4 Swords," and "Ocarina of Time." This is according to a time-line printed in a 2011 Japanese book titled "Hyrule Historia" to commemorate the 25th Anniversary of The Legend of Zelda.