Custom HTMLControl derived from HtmlImage control not visible in VS2008 toolbox

Question

I have a custom control deriving from HtmlImage control which I cant get to show up on toolbox, it says "There are no components in '...\bin\Debug\ImageCustomControl.dll' that can be placed on the toolbox.".

Here is the code for the control:

namespace ImageCustomControl
{   
    public class ImageHtmlControl : HtmlImage
    {
        public override void RenderControl(HtmlTextWriter writer)
        {
            this.Src = "https://somedomain.com" + this.Src;
            base.RenderControl(writer);
        }        
    }
}

Here is a post back from 2003 that says its not possible, but just wanted to know if it has changed since: http://www.microsoft.com/mspress/books/sampchap/5728d.aspx

Thanks in advance.