Dashboard Views: How to modify the menu icon
By default, the menu icon will be the same as the GravityKit menu:

To modify the icon, you can use the gk/gravityview/dashboard-views/admin-menu/icon-url filter, like so:
add_filter( 'gk/gravityview/dashboard-views/admin-menu/icon-url', function( $icon_url ) {
return 'dashicons-privacy';
} );
This will update the menu to use the Dashicons 'Privacy' icon.
The filter allows the same values as the add_menu_page() function in WordPress. See the add_menu_page() documentation for more information.