"no dragon is to be introduced into the stadium for any purpose including, but not limited to, team mascot, coach or cup warmer"
-- the ICWQC rulebook (Pm)
The Mascot Restriction was a motion to restrict mascots to “herbivores, creatures smaller than a cow and nothing that breathes fire”. It was defeated by an overwhelming majority in 1995. Quidditch supporters worldwide have been opposed to any meddling with what they see as a traditional, colourful part of the Quidditch World Cup (Pm).
Lexicon list of Quidditch Mascots
From the Web
Writing by J. K. Rowling on Pottermore:
Pottermore enhanced reading experience: Quidditch World Cup
Screenshots of the original Daily Prophet coverage of the 2014 Quidditch World Cup on Pottermore: Imgur archive