LinkedIn image size is the same as Facebook image size when you share a website link. It’s 1200×628. Usually, it would be a logo image. You would place it in the header using the “og:image” property. For example:
<html prefix="og: http://ogp.me/ns#"> <head> <title>The Rock (1996)</title> <meta property="og:title" content="The Rock" /> <meta property="og:type" content="video.movie" /> <meta property="og:url" content="http://www.imdb.com/title/tt0117500/" /> <meta property="og:image" content="http://ia.media-imdb.com/images/rock.jpg" /> ... </head> ... </html>
If, after you added the image successfully and cleared your website cache, it still doesn’t show, you can use the LinkedIn post inspector to preview it. For more information, refer to the LinkedIn blog post How to clear LinkedIn link preview cache.
To test Facebook URL image use the Facebook Sharing Debugger tool.