Everyone rags on the Nords/Stormcloaks saying they are racist a-holes, but then all I ever hear on here about marriage is people ONLY wanting to marry their race. Love is LOVE in Skyrim. It doesnt matter what race you are.
My Male Redguard married Muiri and lived happily ever after.
My female Breton married Nord Mjoll the Lioness and lived happily ever after
My female Dark Elf married Jordis and they are happily ever after.
My female Breton married Jordis and lived happily ever after.
My male Orc married Nord Jordis.
My female Breton married Sylgia
My female Redguard married nord Mjoll
My Breton dude married Redguard Senna
My dark vampire lord bada$$ cat dude will probably marry Muiri, Dravynea, Brelyna or Borgark.
Just like in real life, you first must choose someone who physically is attractive to you, race doesnt (shouldnt) matter. Then, after that, figure them out to see if they are compatable witih you.
So first, see if the person is hot. Second, see if they are a fit with you. Then, like all the folks I listed above, you will have a happy marriage.