When I started making Icehouse pieces, I quickly realized that there was no reason to stick to the same three sizes in the standard set. Particularly for displaying finishing options, larger pieces might come in handy. So, I calculated the size of a 5-pointer, and made a few of those. A 5-pointer is 1.5 inches across the base, and 2-inches high. Note that the ratio between base and height is not the same for all sizes of piece. As the pieces get larger, they also get squatter. This is true even in the standard pieces.
The picture above shows a pine piece, a red oak piece, and a poplar piece. I have a few pine pieces around, since pine is cheap.
I used the same process for these pieces as I did for the standard size pieces I was making at that time. I cut square rods with the correct cross-section to make the base, then I sharpened the ends of those rods into pyramids using a belt sander. Not the most efficient method, but this was before I had a band saw.