I’m not a marketing expert, but I have gained some ideas over the years which I think are useful and I’ll share some here.
Even non visual products can be promoted through platforms like Pinterest, so it’s always a good idea to have an image associated with, for example, a blog post. In WordPress, use the “Featured Image” option to add an image to the post. Now there’s an image you or anyone else can use to create a link to your post on Pinterest.
It’s worth creating different images for each platform. The dimensions that work for one platform may be cropped on another. If the image you want to use is the wrong aspect ratio, consider creating a collage. I use Google’s Picasa for this. There are also sites like PicMonkey which lets you create collages on-line. (I just discovered Picasa has been retired, which is a shame).
Here are images I created for different platforms:
Pinterest doesn’t seem to have a maximum height. “Skyscraper” images look great here.