Specify task timeout in parallel linq to objects

Specify task timeout in parallel linq to objects

I have a list of Pictures that I want to process in parallel, but with a
timeout. My old code did this by paging through the items and using
WaitHandles, but I want to use the new Parallel Linq or Tasks library
available in .Net 4.
The following snippet is working, how do I add a timeout to it? (Timeout
would be for each task executing, not a timeout for all items to be
processed)
private PictureList FetchPictures(List<Picture> wallResults)
{
wallResults
.AsParallel()
.WithDegreeOfParallelism(10)
.ForAll(delegate(Picture p){