Carrots are an easy decoration that is appropriate for all sorts of cakes: spring-themed, Easter, garden-inspired, and (of course) carrot cakes. All you need to pipe a whole bushel of carrots is stiff consistency royal icing in orange and green, round tips #12 and #3 respectively, a parchment paper square for each carrot, flat toothpicks, and a dusting pouch filled with a 50/50 mix of cornstarch and powdered sugar.
Pipe the stems with the #3 tip. Hold the tip against the surface, squeeze, then pull away, stopping pressure almost immediately. Three or four of these little points look about right.
I piped some royal icing bunnies a few weeks ago; if today's project goes missing, I'll know where to look.