User Control that allows users to select multiple images

I have been trying to figure out a way to do this, and have come to an impasse. I am trying to create a user control that allows the user to select any numbers of images (like 20 photos max) and have them displayed in a user control because they need to be formatted in a certain way. I dont want to create 20 image selector dialogs, so what would be the best way to implement this so that a user could select a gallery or select a group of pictures and then allow me to do some things to them to display them properly.