Additional Ideas:

Incorporate horses? Dorothy, the Tin Man and the Lion are taken into the Emerald City via horse and buggy. The horse keeps changing color. Is there something we can do with this?

An idea to use a large, tall glass vase and use it as a dimly lit lamp. (it's possible, I saw something like it online). Incorporate an emerald green lamp shade and emerald beading.

An idea in the main ballroom to drape emerald green fabric from the ceiling to give the true feeling of being engulfed in an emerald room.