I use the leaflet and the getfeatureInfo function to display the data of a wms layer belonging to the geoserver, I want to customize the display of retrieved table: I use this plugin https://gist.github.com/rclark/6908938.
If you have access to the GeoServer instance you can control the style and layout of the response to a getFeatureInfo
request using templates.
If you only have access to the endpoint then try requesting the response in application/json
format and then use JavaScript to display the information in whatever format you like.