My 3 year old niece wanted a Tinkerbell Fairy Garden birthday cake so I decided to try a little royal icing work for the first time. Some of the more intricate pieces (butterflies, ladybugs, and fancier drop flowers) I had to buy from a local cake supply store and the Tinkerbell candle and #3 candle came from there also.
I stacked two 9" layer cakes (one chocolate, one vanilla) and iced them in homemade green butter cream (crumb coated first). I used Americolors icing gels. I like those better over all than Wilton gels. I used a skinny serrated pumpkin carving knife and cut a little "pond" into the top, and filled it with sky blue colored icing, then swirled a little darker blue frosting, then Wilton sparkle gel color tubes from the cake store.
I piped a vine pattern all over the sides of the cake with a slightly darker green than the cake frosting (mistakes covered with my royal icing drop flowers). The tree trunk was a little chocolate cake baked in a recycled tomato sauce can. Then I took some rolled out brown Wilton fondant and draped it on the little cake to make it look like a tree with the leftover folds at the bottom making nice "roots". Any rough spots at the edges is covered with the icing grass.
I made the top of the trunk by using fondant rolled out, cut in a circle, colored with Wilton ivory. Then I took a teeny bit of brown color gel and diluted it with lemon extract and painted a very subtle circular pattern to make it look like tree rings.
The mushrooms are also fondant colored with the ivory color gels and with the dots painted on lightly the same as the tree was. I made a little blue bird out of fondant. The cake looked kind of rough and I worried it wouldn't come together, but once I piped grass on it and added the royal icing flowers everywhere plus all the little decorations it just fell together.
I used the Wilton site recipe for Royal icing using meringue powder. Then I used Americolor gels to color small batches pink, purple, yellow, and green. Using a small star tip I just made drop flowers and piped yellow centers and let them dry over night. I started the frosting on a Friday night, and had to have the cake completed by Sunday afternoon.