I tried to add a card cover to my card and thought that helping the cropper would give good results. So I uploaded an image of 320×100 (see these specs). The image gets cropped to a 70×50 image and only shows a very small piece of the original image.
Question: What is the size to upload if you want the complete image to be shown as a card cover?
Best Answer
I like to create a 336x140 png using a Photoshop template to identify the 276x140 safe zone at the center of that image where I know cropping won't occur on the subject. It is not necessary to have a graphic of this width, but I find a wide-screen graphic to be reusable in other areas besides Trello.
I've uploaded the Trello Card Cover Preview Template to my website: http://www.justinreinhart.com/2012/07/19/trello-card-cover-preview-template-for-photoshop/