Can I create a new dock item and drag desktop shortcuts to that item? How can I change the icon (e.g. i want to change the internet icon to the firefox icon)?
Thanks

You can create a subdock to contain those shortcuts or create a folder and have a dock item that links to the folder. Changing the icon of a dock item is possible by right-clicking the icon, going to dock/shelf entry properties and change the icon.

Or you can just drag & drop an .ICO or .PNG file of your choice *into* the shortcut in the dock. That easy.