Quote - Yes shiva22 :)

File--->Import--->Background Picture

Let it resize your screen to match the BG size, this will get you the proper proportions. Resize it down (Window--->Document window size)  from there to fit your screen and comfort level :)

When you render,  render (Render--->render options--->New window) at the same size as your BG. The bigger the better.. When your picture is finally finished and all merged, you can reduce it's overall size to print or upload. The shrinking process makes the anti alias 'blend' in seemlessly.

:)

Thanks guys, I figured it must be possible.