While looking for something to go into the bottom of vases to hold flowers for my daughter's wedding and keep the costs down, I ran across some bubble wrap laying around that was shaped like ice cubes. I cut two piece about 4 inches wide and 6 inches long. I laid each piece in the bottom of the vase and up the sides on either side of the vase. When I added the flowers to the vase, it looked so very much like the vase held ice cubes and was very attractive. I got loads of compliments on the flower arrangements.
Although not a great picture, you can at least get an idea of what I am saying.
By gem from Gordonsville, VA