Using kitchen shears, snip off a thin strip from the side of a marshmallow to make a petal. Work your way around the marshmallow to snip off more petals. Repeat with 23 more marshmallows. (You'll need 10 to 12 petals per cupcake.)
Snip a thin round from the top and bottom of the remaining 6 marshmallows. Press the 12 rounds cut-side down in the yellow nonpareils to coat.
Arrange the marshmallow petals on the cupcakes, then place a nonpareil-covered marshmallow in the center of each.