Why are the images scaling to 50x 50 pixel?

Hi again - we had some issues with our marketpress/gridmarket site http://www.papercraftkitworld.com and had to replace some files, now the same problem is back again with the images staying at 50 x 50 pixels no matter which store setting I choose on the Presentation page.

I paid for this to be fixed by a web developer and he said he altered the code in :

We cannot contact him now and we don't know what changes he made.

So why are all my homepage product images not changing to the size I set them at 150 x150 pixel?