If there is one question that we are asked more often than any other, it's "How big should I make my images?"
Short answer: As big as you can, and as consistent as you can*
(*for your product and slideshow images)
Shopify have a great little article which explains this concept brilliantly!
Image sizing, image aspect ratios and proportions seem to confuse more store owners than any other issue. We all know that a picture can tell a thousand words and that good images can transform your store, after all it's the only way an on-line customer can see what they are buying, so what size should your images be?
Your product images can be any size up to 2048 by 2048 pixels, or 4.2 megapixels. A good guideline size for product images is 1024 by 1024 pixels. They don't have to be square, but it is best to make them a consistent shape.
Product images on the collection page and homepage
A consistent aspect ratio, or or height-to-width ratio will make the products on your collection and home pages look much neater.
Slideshow and banner images
We generally recommend using images 2048px wide in your slideshow. It's really important that all your slideshow images are the same height to avoid the appearance of the screen "jumping" when changing slides.
Our most commonly asked question for slideshow images is "can I make the image smaller, it takes up too much space on the page". This is down to the shape / aspect ratio of the image. A letterbox shaped slideshow image will take up less screen space than a square one.