How can I pass additional parameters to predicate functions?

No, but you can do this:

public Comparison<T> MakeComparison<T>(object extraParameter)
{
    return
        delegate(T x, T y) 
        {
            // do comparison with x, y and extraParameter
        }
}

Simple capture the variables you need when you declare the predicate. Eg:

int i = 0, j = 10;

array.Sort(x => x > i && x < j ? 1 : -1);