Don't forget the greenery! Insert a single flower here or there, framing in a rose or cluster of stock flower. Gracefully drape flowers like the seeded eucalyptus so it falls over the edge of the cake.
It looks more natural if the clusters are made up of different sizes and amounts of flowers. If every flower cluster is a rose, stock and specific amount of wax flower, it is going to take on a rigid look.
You can add crystals, pearls and other decorative accents, but always remember to tape them to wooden toothpicks and keep non-food safe items from touching the actual cake surface.
I mix up sizes of flower heads. These are both roses - but one is a standard rose and the other is an open spray rose.
Move down the cake, filling in where ever you placed the toothpicks. (Remove those toothpicks as you design).
I generally like decorating all sides of the cake, front, sides and back for a uniform look. You can just do a 3/4 look, making sure that all sides visible to the guests are decorated.
Smaller clusters or single flowers with a small leaf or sprig of greenery works well on the smaller top layers.
The clusters can get bigger as you work your way down to the bottom (larger) layers.