Hmm... I have two fan characters, so they're different.
Sharo/Shattered Rose (Pegasus version) has the mark of a flower with three of its petals falling to the ground. Sharo herself is a dark-red Pegasus with a black mane, tail, and wings. She has green eyes.
Spearmint, on the other hand (Unicorn) has a mark of two spears crossed in front of a maple leaf. Spearmint is a mint-green colt with blue eyes and a white mane and tail.
Edit: I created another character. Lightning Flare has a mark of a lightning bolt and a purple quill crossed together.