I'm surprised this rumor didn't come up already here: Karen Gillan's character might actually be Marvel's newest character, former Spawn ally/adversary Angela, which would be freaking awesome.
Angela had fallen into obscurity. Her first appearance could easily be gotten for $5 at any show. I sometimes saw Spawn #9, in F/VF shape, in $1 bins even.
I hope this turns out to be fanboy wankery. Don't care for Angela to be in the movie. She's an on loan character, they should use a proper female character from their library.