Thumbnail size
See this page http://fertimac.com.br/vanleeuwen/fleur-en-vogue/, the thumbnails have a standard size of 150px X 150px, realize that the result does not look good, would have to increase these values to 300px X 300px?
Comments
To change the size of the images on portfolio/blog/shop please navigate to theme options>blog,portfolio&shop>featured image.
To change the size of the default wordpress images please go to settings>media.
To change the woocommerce images size please go to woocommerce>settings>products>display.
There set the desired image size. Remember to read the notice at the bottom of the page regarding thumbnail regeneration.
thanks