Michelle,
I can only give you my opinion based on experience. If a topiary is going to be three or more feet tall, then creeping fig is the plant to use. However, if the topiary will be under three feet then I prefer to use one of the Rosemary prostratus varieties (trailing type) for form and tidyness.
I assume that this is a permanent outdoor topiary. R. prostratus takes very tight shearing well. Over the years I have developed the following method. Around the topiary form place eight tip end trailing Rosemary cuttings which have been dipped in rooting hormone. Rosemary roots easily in this manner, ever in hot sun. Yes, this sounds like a lot of plants, but your topiary will fill in quickly and never look thin. At first, when the rosemary starts to grow you will have to encourage it to grow on the form by securing each stem with a twist of raffia. Once started it will cling and mound to itself.

I was pruning one of mine today. It has bloomed all winter and just shapes up beautifully. You might want to try this method.

I agree with the first post, rosemary is a great plant, one that I use a lot. Another plant, just to give you options, that I also use alot is Dwarf Myrtle, Myrtus communis 'Compacta'. Very fine textured, bright green leaves that works well for small topiaries tosizes as large as 5 or 6 feet.

Here is a link that might be useful: Chris' Topiary Nursery