Please have a look inside the WC plugins folder and look under templates folder. In that folder you will find all the necessary template files that generates most of WC including the related products part.
Then you can copy it out and put into your theme folder so your changes will not be affected by updates. Here is a link that will show you what to do. http://docs.woothemes.com/document/template-structure/
I find this http://docs.woothemes.com/document/remove-related-posts-output/
I don’t really want to remove related products, but it’s the only solution instead of having BIG images for Related Products
