What white looks good with Peppercorn?
You can go with a brighter white like Extra White or Highly Reflective White or one that is a little softer like Pure White.
Another great option for trim is to use the wall color on it. You can use a different paint sheen so that there is some variation.
By using the same color on the trim as the walls there is no break in the color to draw your eyes. It allows the accessories in the room to be the star of the show.