Threading in custom Usercontrol

public partial class DesignListView : FlowLayoutPanel
    {
        public DesignListView()
        {
            InitializeComponent();
        }
        private List<String> fileList;
        public List<String> FileList
        {
            get
            {
                return this.fileList;
            }
            set
            {
                this.fileList = value;
                PopulateThumbnailInThread();
            }
        }
        public void PopulateThumbnailInThread()
        {
            Thread t = new Thread(new ThreadStart(PopulateThumbnails));
            t.IsBackground = true;
            t.Start();
        }
        public void PopulateThumbnails()
        {
            this.SuspendLayout();
            this.Controls.Clear();
            this.ResumeLayout();
            if (fileList == null)
                return;
            for (int i = 0; i < fileList.Count; ++i)
            {
                ThumbnailDisplayControl tdc = new ThumbnailDisplayControl(fileList[i]);
                tdc.MouseDown += new MouseEventHandler(tdc_MouseDown);
                AddControl(tdc);
            }
        }
        public delegate void AControl(ThumbnailDisplayControl tdc);
        public void AddControl(ThumbnailDisplayControl tdc)
        {
            if (tdc.InvokeRequired)
            {
                tdc.BeginInvoke(new AControl(AddControl), new object[] { tdc });
                return;
            }
                this.Controls.Add(tdc);
        }
        void tdc_MouseDown(object sender, MouseEventArgs e)
        {
            //Displays the selected design
        }
        
        public event DesignSelectedEventHandler DesignSelected;
        protected virtual void OnDesignSelected(DesignSelectedEventArgs e)
        {
            if (DesignSelected != null)
                DesignSelected(this, e);
        }
        
    }
    public class ThumbnailDisplayControl : PictureBox
    {
        // provides image with design and its name.
    }
    public class DesignSelectedEventArgs : EventArgs
    {
        // delegate properties n stuffs
    }
    public delegate void DesignSelectedEventHandler(object sender, DesignSelectedEventArgs e);