This is a great gift ! In the dark, these flames really glow in the candlelight. The effect is most intense if you use a highly textured glass. The structure should not be too coarse, so that the light of the candle refracts on as many points as possible. Just hold your pre-selected glass against the light of a candle and see if the effect is good.
In a similar form and made of green glass, you can also use this design to represent conifers. There are many possibilities...