After Freya is killed by a bloody slice down her back, she falls forward. Her back shows neither a cut nor blood on her vest.
Freya is asked if her Foresight can see backwards, but Freya did not have the power of Foresight - that was Frigga, Thor's stepmother. Freya was the goddess of love, passion, fertility, and war in later days.
When in the beginning of the film they are rowing the ship, they are moving the oars in a way that would make then actually go backwards.
When one of the Nordic soldiers opens his mouth you can see a gold crown shining brightly.
Throughout the film, the lead females are frequently shown to be clearly wearing pale colored lipstick.