Elwing: I think she'd be Arwen's second cousin? They're both great-granddaughters of Galadhon. But I think you generally take only the closest relationship, right? Otherwise, the Hobbits - whooo-ee!
According to the
coefficient of relationship page, second cousin and first cousin twice removed are identically close (3.125%). So Elwing would be a viable answer - were she not her great granny.
Pharazon is also an interesting catch, but still very distant by comparison.
Fallen Banners: sure, but I can only find one person whose closest relationship to Arwen is at the first cousin twice removed level. It doesn't matter who you ship them with, that person would be more distant. Or dead.
hS