So I'm making 2 cakes next week for my son and neice's combined bday. I'm going to be making 2 different 1/4 sheets. Both will be done with a personalized edible image. For my son, its Thomas the Train, and my neice its My Little Pony. SO I need help with ideas on what to do with the sides and borders. Want something fun, and will be using only buttercream. I would appreciate any ideas/pictures for help. Thanks in advance

Railroad track around the sides of the Thomas cake. With maybe a green leaf border.

For My Little Pony, rainbow stripes on the sides, with a star border.

Holly