Go look at lyn's mask in winning outfit.
And now Google for "Marth Fire Emblem mask".
"Further, any Costume Design that contains trademarks, copyright - protected or other proprietary materials for which the Entrant has not obtained appropriate assignment of rights will be void. "
Commenters also found parts stolen from:
Rage of Bahamut - heavly "inspired" clothing for Jin
Touhouvania - traced hairstyle and hairband
Summary from @shinnabuns: