You want the child to feel like royalty, therefore more metallic colours will fit the theme. Princess characters are not necessary for this theme but if your child is fond of one then try to include it. The children themselves can dress up and be the princes and princess, which we are sure they will enjoy. The colour palette is standard for this sort of theme, whatever colour you have in mind, we advise using a myriad of shades. Progressively getting darker.