My daughter who is now 8 comes up with some, let's say, challenging birthday cake ideas and I have mastered them all! I told her it will be interesting when she actually stumps me as to how to make it! LOL! Anyway, here are a few ideas (some not as easy, but it might help):
Candyland game board cake
polka dot cake (I used Necco waffer candy for the dots)
vanilla, chocolate, strawberry cake (she wanted it to look like the ice cream in the container)
banana split cake (yes, like a real banana split, but NO bananas)
Doggy Bone shaped cake
For my daughter's first birthday I did different size cupcakes decorated like flowers. I set them on a tiered (wedding) type stand with cut out petals that covered the plates.
I have also made for one of my husband's employee, a birthday cake that looked like two presents wrapped together. The ribbon was fruit by the foot.
Hope this helps!