// 全局变量，储存图片
private SortedDictionary<string, Image> slist = new SortedDictionary<string, Image>();

private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
{
    if (e.ColumnIndex == 显示图片列的索引)
    {
        if (e.Value is string)
        {
            // 图片路径
            var key = (string)e.Value;
            Image img;
            // 保存在全局变量中，避免重复加载
            if (!slist.TryGetValue(key, out img))
            {
                img = Image.FromFile(key);
                slist.Add(key, img);
            }
            e.Value = img;
            e.FormattingApplied = true;
        }
    }
}

------解决方案--------------------

C# code
        private void demoGrid_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
        {
            if (demoGrid.Columns[e.ColumnIndex].Name.Equals("Image"))
            {
                string path = System.Windows.Forms.Application.StartupPath + @"/1.gif";
                e.Value = GetImage(path);
            }
        }


      public System.Drawing.Image GetImage(string path)
        {
            System.IO.FileStream fs = new System.IO.FileStream(path, System.IO.FileMode.Open);
            System.Drawing.Image result = System.Drawing.Image.FromStream(fs);
            fs.Close();
            return result;
        }