I've been looking all over online but can't seem to find a clear answer as to how to make realistic looking ice cubes with isolmalt.
I don't know if that link will help or not but it is a link that tells you how to make isomalt snowflakes and they look like ice to me. Perhaps you could make the icecubes the same way using a different mold?
I used the wilton silicone brownie pan (it has a bunch of little squares on it). I picked it up at Michaels. I melted the isomalt, poured it into the squares, let them set up, then popped them out. I have also seen silicone ice cube trays.
This is the brownie pan, http://www.wilton.com/store/site/product.cfm?id=AF414343-1E0B-C910-EAF4100780D53DC6&killnav=1
Another option is to use the silicone ice cube trays and pour the isomalt into there. I bought mine from Target. I also use them to create "Cube" of isomalt so I have small amounts to color.