Although B looks more organized, A has an advantage that all pics -I assume that the pictures are links to categories- are nearly the same size.
Having a category dominating the page will give a false impression that this category is what the website is all about and the others are just fillers. In other words; it will make that category seam as your specialty and other categories will seam less important.
I believe if you used the concept in A, while adding titles to the pictures and maintaining a golden ration for all pics; the site will be more balanced and appealing.
Your mileage may vary...