From Neil Gaiman and Dave McKean (of Sandman fame) comes a new movie called Mirrormask, and damn, if it doesn't have that rich fairy-tale feel that's so ingrained in Planescape. Take a look at the preview. The spider made me think of some new type of Modron, and the Dark Lands in general could fit into Planescape perfectly (there's so much room in infinity!).
The problem with fantastical movies like this is that the world can often overpower the characters and the plot. In labyrinth, it was David Bowie's character that made everything hum (so to speak), and there needs to be a strong personality to anchor the story to reality. Here's hoping the acting can match the set design.
Dunno, I'm a huge fan of Gaiman's work, but I don't really see much of a connection between Mirrormask and Planescape...