The Japanese website for Hyrule Warriors recently showcased some of the costume DLC for the game.
Right now, the DLC is only confirmed for the Japanese version of the game. There are multiple planned editions for the Japanese version of the game called the Premium and Treasure Box. These outfits are part of the courage and wisdom costume costume sets. Presumably a power costume set is also planned in the interest of finishing out the Triforce. More DLC costumes are planned, but these are all that have been revealed so far.
For more on Hyrule Warriors, check out trailers for Link wielding the Master Sword and the Fire Rod, the appearance of Lana, Zant, And Agitha, Zelda, and Impa. For more, check out our hands-on impressions from E3, an interview with the team, and the title's E3 trailer. Hyrule Warriors will be out on September 26 on Wii U.