How To Center Odd Number of Categories or Products

Hi,
I am developing a store using mystile theme and there are 3 product categories. and they appear aligned left with space for a 4th which is obviously not there.

On lower width browsers the it shows 2 columns of images and with the 3 categories the third is aligned left below the first 2.

This layout looks a bit and it would be nice to align the categories and their images centred on the page whatever browser width the user was viewing the page from.

I found the following page but the .products.ribbon style in woocommerce 2.014.

Any advice would be appreciated.

Thank you.

Bharat