That is not a style element your talking about. Your electing to show 3 rows. You can try 4 rows like so Members Galleries - ReefTalk Gallery
Your talking about html code not stylesheet classes. Each td in your case one third of the space and then with that td the content is aligned center and vertically aligned middle in a table which is 90%. You can make that 90% 100% if you want.
That is the showgmall template.