If you are looking for a simple and free way to add a table to your Stacks page, you can use one of these, just unzip them and copy them into ~/Library/Application Support/RapidWeaver/Stacks before starting RapidWeaver:
There are two variants:
With custom Stack Elements in each cell:
With text in each cell:
Both Stacks Element allow you to configure the columns and rows of your table and you can specify the colors for the header cells and the lines:
If you would like to add an own style, just open the .stacks file and edit the styles.css file.