One of the best usability features added to Dynamics 2013 was addition of the Create button in the navigation bar. As part of the new user experience (UX) enhancements it allows new records to be added from anywhere in the system without leaving the current form. A typical scenario is the logging of a new phone whilst working on another task.
If you want configure an entity to appear as a quick create options then customize the entity and check the “Allow quick create” option under Data Services as shown below. The entity must have a quick entry form to appear.
For custom entities I would suggest that you upload an icon for your custom entity to enhance the user experience.