Last year for Christmas I wanted to make my son some of his own "boyish" dress up clothes so I borrowed my little neighbor boy's (Jack) costumes to make up my own patterns. I pretty much laid out his costumes on white packing paper and traced around the shapes of the different parts of the costume. Then I attempted to allow about 1/2" seam allowance. Not everything turned out perfect but pretty darn good for some new dress up clothes. This is what I came up with for my little guy.
Peter Pan or Robin Hood
Knight in tunic with hat
Pirate with sash
All decked out with skull and cross bones