Something you want to see incorporated into the story line that deals with your character that everyone will be a part of.

ex: Hawkeye used to be a criminal, but left the life to join SHIELD. But now his old gang wants revenge. Can his team still trust him?
Wanda's father is Magneto. When she finds out she decides to join the Brotherhood of Mutants. Her team members go to find her and remind her of who she really is.
The 10 rings steal some of Stark's weapons. He goes to get them back. Shenanigans ensue. 

Stuff like that. Things I can use to add character development and add a personal touch to the plot.