Adding colors or using different types of sugar such as maple syrup will produce different effects. You might also want to try adding flavorings like peppermint or vanilla.
Crystals need a rough surface to grow on according to Sugar Craft, so they recommend experimenting with things like cotton string, sticks and anything that is course.
Crystal Clear Science Experiments recommends experimenting with different cooling times using a fan to cool the sugar solution faster. Note the size of the crystals.
Try weaving string through a pan and pour "Super Saturated Solution" in. Let it set for a week and see what happens. See what would happen if you used fishing line instead of cotton string.
The best part of a Rock Candy is eating it. Use it on a cookie, stir your tea with it or just eat it right off the string.