My OC is a Changeling, so he doesn't have a Cutie Mark. But I am making him a pony form, so this should be useful.
OC/Ponysona Name: Cocoon
Talent(s): He is quite good at defensive magic, mainly shields and sleep spells. He is also great at hiding his true emotions, he always has a straight face.
Passions/Personality: He is dark and gloomy almost all of the time, though he doesn't show it, he doesn't care about others and suffers from PTSD. He doesn't really have any passions, due to the fact that he's been living in a forest for about 10 years, so his only real goal in life is to survive.
If you want any more information, you can check out the OC page in my signature.