The config.php file is working fine, I was checking inside there to see if I could have changed any of the display settings!
That has worked, thank you! However, one mystery remains: All the images I have per product show up tiled on the product page - I thought that one image (the top image in the 'list') would be the main image and the other images appear as thumbnails, viewable when clicked on. Now, if I have e.g. 4 images all 800px in width, my page is verrry long.