c#實現圖片堆疊及如何做Resource讀取圖片功能

我想透過Window Form app 去做個桌面程式。它能夠讀取圖片像C#內Resource讀取圖片那樣 以及能做到圖層堆疊像Photoshop。但是目前還無法實現外部讀取圖片功能如下圖所示我知道C#有OpenFileDialog class 可以達到做外部功能可是目前還需實現點選圖檔
將圖檔存進自行定義結構當中，然後能像c# resource直接將圖片叫出來用。C# 可以透過將PictureBox 堆疊在Panel 將Panel BackColor 設定為Transparent實現透明圖層概念但是我自己寫功能無法實現private void AddNewPhotoToolStripButton_Click(object sender, EventArgs e)
        {
            /*
            var fileContent = string.Empty;
            var filePath = string.Empty;            using (OpenFileDialog openFileDialog = new OpenFileDialog())
            {
                openFileDialog.InitialDirectory = "c:\\";
                openFileDialog.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*";
                openFileDialog.FilterIndex = 2;
                openFileDialog.RestoreDirectory = true;
                if (openFileDialog.ShowDialog() == DialogResult.OK)
                {
                    //Get the path of specified file
                    filePath = openFileDialog.FileName;                    //Read the contents of the file into a stream
                    var fileStream = openFileDialog.OpenFile();                    using (StreamReader reader = new StreamReader(fileStream))
                    {
                        fileContent = reader.ReadToEnd();
                    }
                }//end if
            }
            MessageBox.Show(fileContent, "File Content at path: " + filePath, MessageBoxButtons.OK);
             */
            Panel backGround = new Panel();        
            backGround.Location = new System.Drawing.Point(67, 57);
            backGround.Size = new System.Drawing.Size(800, 480);
            backGround.BackgroundImage = Properties.Resources.fullground;
            backGround.BackColor = Color.Transparent;
            Controls.Add(backGround);
            backGround.BringToFront();
        }        private void OvelayPhotolStripButton_Click(object sender, EventArgs e)
        {
            PictureBox a =new PictureBox();            
            a.Location = new System.Drawing.Point(200, 107);
            a.Size = new System.Drawing.Size(200, 50);
            a.BackgroundImage = Properties.Resources.needle;
            a.BackColor = Color.Transparent;
            Controls.Add(a);
            a.BringToFront();
        }
    }目前結果如下圖請問該如何解決圖層透明堆疊問題圖片都是png檔