Björk will play herself on Icelandic Television in a serie called "Dagvaktinni". After acting in Lars von Trier's "Dancer in the Dark", and much earlier in the Bros. Grimm movie "The Juniper Tree".
And she played herself already on the catwalk in Robert Altman's "Prêt-à-Porter" (1994):
www.youtube.com/watch?v=iN89RJLqBC8