According to Wikipedia : Niflheim ("Land of Mists") is the realm of ice and cold in Norse mythology. It is located north of Ginnungagap and there dwells the hrimthursar (Frost Giants) and here is also located Hel. The tree Yggdrasill has a root here in the spring Hvergelmir, and it is gnawed away at by the serpent Nidhogg.
Niflheim is ruled by the goddess Hel, daughter to Loki by the giantess Angrboda. Half of her body is normal, while the other half is that of a rotting corpse. Niflheim is broken into several layers. One level designed for heroes and gods, where Hel would preside over the festivities for them. Another is reserved for the elderly, the sick, and those who are unable to die gloriously in battle and enter Valhalla. The lowest level resembled the Christian version of Hell, where the wicked are forced to live forever.
Well.. I love the concept that souls of died people go to Niflheim in form of butterflies. I saw this somewhere and I really like it. Also colors: I don't see 'death' as the end of everything. I believe in afterlife, reincarnation etc. so pink ( as hope and love) and especially violet ( color of highest chakra ) are important in this work.
Anyway.. I hope You like it..
and You are not to tired reading this description
*EDIT: -Niflheim wallpaper-