You can use Automator to create contextual menu item plug-ins for the Finder. Then, when you Control-click on a folder or file in the Finder, you will see a command in the menu to make a disk image or archive using DropDMG. To set this up, first create a new workflow in Automator. Then drag the DropDMG action into it, choose a configuration, and then choose Save As Plug-In from the File menu.