Decorate cake. Prepare decorating bags separately with tips 5, 8, 12, 14, 18, 32, 2D, 101, 352, 366 and 81. Fill with desired icings, striping some bags and using solid colors in other bags.
Using pull-out star, pull-out leaf, dot, petal, leaf and star techniques, pipe succulents around top edge of cake and along bottom edge of cake.
Prepare decorating bag with coupler and remaining white icing. Using tip 1, pipe small dots on pull-out star cacti. Using tip 3, pipe dots around sides of cake.