Focus on competition:
* A verbal gladiatorial arena
* A battlefield of words
* A linguistic wrestling match
* A mental marathon of spelling
* A game of wits and vocabulary
Focus on the challenge:
* A verbal tightrope walk
* A test of mental agility
* A linguistic maze
* A journey through the dictionary
* A climb up the word ladder
Focus on the participants:
* A chorus of spellers
* A symphony of letters
* A team of word warriors
* A gathering of linguistic champions
* A showcase of spelling prowess
Focus on the experience:
* A rollercoaster of emotions
* A whirlwind of words
* A dance of letters
* A magic show of language
* A glimpse into the power of words
The best metaphor will depend on the specific message you want to convey.