You can link to your Google Drive documents and images from the Task Properties dialog.  

• Select a task in in your project.
• Open the Task Properties dialog (Either double click the row OR highlight task and select the gears icon on the toolbar)
• Select the "Links" tab
• Click the "Add" menu button.
• Select "Google Drive", the Google Drive file selection dialog will open.
• Select the document or image you want to link.