What is the optimal display page art size?

As title, on the display page where you upload a piece of art for your campaign what is the optimal pixel ratio to avoid having any white space on the sides? Before that last major update I believe it was 300 x 512 pixels as detailed on this wiki page&nbsp; <a href="https://wiki.roll20.net/Image_Best_Practices_for_Roll20" rel="nofollow">https://wiki.roll20.net/Image_Best_Practices_for_Roll20</a> But that doesn't work anymore, I was wondering what other people are using.

If your window width is greater than or equal to 1200px, the column which includes the campaign image is 780px, and the image has a maximum height of 400px. There's 15px of padding on each side, so the image is limited to 750px wide. The layout changes somewhat at other window resolutions.