Hi yuki,
It sounds quite sufficient liao. You want to emphasize the theme without overdoing it otherwise it'll not stand out.
One thing I can think of. Maybe you want to select a wedding favor that is see-through to have the crystal effect? eg, transparent wedding bells or shot glass even?
Actually, crystals on WG will be nice at night coz the lights will make the crystals "sparkle". On close-up, maybe not as nice though.
Your crystal theme also conjures up glass slippers (ala the cinderella fairy tale). I also get reminded of crystals of snow flakes when I think of crystals.
I believe your banquet venue has crystal chandeliers? Otherwise, it's not so easy to pull off this theme.
The other thing you can consider is the chinaware that your hotel is using for the banquet. See if they can serve the dishes in transparent plates instead of the usual white ones. Or provide your guests with 1 piece of crockery that is transparent! Again, the idea is to highlight without overkilling the theme.