Looking at the quiz the source code, the question for which the mystery new character is a potential answer is "Who should be the MC [for your wedding]?", and the quiz aims to determine your dream wedding location.
Answers:
That's Celestia, Zecora, mystery-character, Chief Thunderhooves. Unfortunately, the files are called things like 'q2q7c3.png' so we can't find out this character's name. Judging by the different species of the characters here, he's probably not a pony though.
The source code for the quizzes is here.
Here are all the questions for quiz 2:
Spoiler
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1) Which of these rings would you like to be used for wedding?
2) Which of these bouquets would you like to be used for the wedding?
3) Which of these cakes would you like to be used for the wedding?
4) What should be the music for the wedding?
5) Where should the wedding take place?
6) What kind of punch should we serve?
7) Who should be the MC?
To get answer number Y to question X, go to the URL http://wedding.mylittlepony.com/images/quiz/q2qXcY.png - the new character is X=7, Y=3.