I have been trying to upload my designs and even though they fit within a 4500px x 5400px canvas, they are not being accepted because it keeps saying "Please upload a file matching the artwork dimensions below." It is within the required limit but not those EXACT measurements. Then I did a test image with a border that stretched to the edges of the canvas and was exactly 4500px x 5400px. That seemed to work. But what if you don't want your design to be that big? I must be missing something here.