Can someone give some examples of Mormon symbolism from Twilight?

sure! no prob...*ahem*
okay, during the whole "lets-make-a-gazillion-vampire-children-and-kill-everyone" with the three girls (jasper and alice's story of something) the girls keep going on about how they'd have "special privilages" if their army of guys did everything they wanted.
it's kinda mormon, but instead of a guy marrying 50 girls, its a girl "marrying" a gazillion guys.
hope it helped-im writing what i remember...

the whole, "lets have sex after we're married" and also "Oh, i'm not aborting the baby even though it's killing me, and if I don't abort I will die with the baby"

Then again, a lot of christian religions believe this.

Well, Mormons believe that Native Americans are descendants of the lost tribe of Israel, so there's something about that with the Quileutes. Then there's the protagonist vampires having a big family. Someone also suggested that Bella becoming a vampire was a metaphor for going to Heaven.

The whole vampires getting paired up A.S.A.P. thing. Along with the imprinting situation.