I also recommend that you change your render settings  to "Render over black background."  This will prevent you from having an ugly 1 pixel grey border around your image. There will still be a 1 pixel black border, but that looks more like a shadow than a border, and is much nicer.

However, when you are wanting to render something like a bride in a white dress, I suggest rendering over a white background so that the pixelation will blend in.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi