How can I update the Facebook thumbnail image for my Wix site?
The thumbnail image will appear when your site is shared on Facebook. The images give your visitors another way of identifying your brand.
To change your thumbnail image: From the left side of the Editor, click Settings > click Social Settings > click Upload Thumbnail > choose an existing image or click Upload Images > click Choose Icon.
According to Facebook's specification, the minimum dimensions for Thumbnail images are 200px*200 pixels, and the maximum dimensions are 1500 pixels*1500 pixels. We recommend that you don't exceed 1000 pixels*1000 pixels.
Keep in mind that it may take Facebook some time to process your site's information. In order for Facebook to process your site sooner, you can use Facebook's Debugger here. Simply type your site's URL in the Input URL field and click Fetch new scrape information.