FOR DECORATIVE ICE CUBES: put small chunks of fruit or mint sprigs into an ice tray, fill with water and freeze.
Serve the ice cubes directly in drinks, or put them out in a glass bowl or ice bucket with tongs.
FOR THE DECORATIVE ICE MOLD: you will need a glass bowl that is smaller than your punch bowl, plus a second shallow container of equal volume.
Fill the shallow container with water and let it sit at room temperature for 15-30 minutes, stirring it from time to time to get rid of any air bubbles.
Line the bottom (but not up the sides) of the empty glass bowl with fruit and/or flowers of your choice.
Take a tablespoon or so of water from the shallow container and pour this water over the fruit/flower layer, then put the glass bowl in the freezer, leaving it there until the fruit/flower layer is anchored in ice.
Next, pour another tablespoon or so of the reserved water over the first (now frozen), and allow this to freeze; continue adding water and letting it freeze until the fruit/flower layer is just barely covered in ice.
Now start going up the bowl, laying fruit and/or flowers against the side of the bowl, and pouring water over them a little at a time, allowing the water to freeze to anchor the fruit and/or flowers against the side of the bowl.
Continue adding water and allowing it to freeze until the bowl is full of ice.
When you're ready to use the mold, let the bowl sit at room temperature for 15-30 minutes; or alternatively, put it in a slightly larger bowl containing warm water for a couple of minutes.
When the ice has melted just enough so that it's no longer stuck to the side of the bowl, invert the whole thing inside your punch bowl; the result will be a mound of ice with fruit and flowers all over its surface (Note: when you pour some punch over it, the ice surface will become clear, though it's usually opaque when it first comes out of the mold).