Consumers love online shopping for its convenience but it doesn’t lessen the sense of skepticism before making a purchase. It’s hard to make a decision to buy an item online when you cannot feel it or try it on. This is why product photos have a significant impact on sales and are essentially the make or break aspect during the shopping process.
Images of your products and interface is a very important for your site and product impression. So pay extra attention to your images. Product images should be with good quality and resolution (at least 600px).
Depending on the products that you sell, you can choose the type of product images. They can be rectangular (a form well suited for clothing) or square (which is best for shoes, accessories, electronics, etc.).
Here is Alysum official and always updated information about images configuring http://alysum.promokit.eu/documentation/#images
By default Alysum theme has the following proportions of product images 0.61:1.
If you don't want to see white margins then your images should have white background or should be with the same ratio as rectangular thumbnails.
We advice you to set the rectangular image dimensions according to the default Alysum settings:
Use the online ratio calculator to know the exact image size you can use: http://andrew.hedges.name/experiments/aspect_ratio/
By default Prestashop uses only .jpg (transparent background support only .gif and .png image types). But if you need transparent background for logo here you can find the solution