Thread.Sleep() in C#

I want to make an image viewer in C# Visual Studio 2010 which displays images one by one after seconds:

i = 0;

if (image1.Length > 0) //image1 is an array string containing the images directory
{
    while (i < image1.Length)
    {
        pictureBox1.Image = System.Drawing.Image.FromFile(image1[i]);
        i++;
        System.Threading.Thread.Sleep(2000);
    }

When the program starts, it stops and just shows me the first and last image.