As Durgesh mentioned, you will NEED a ThingMark - but you should be able to customize them.
However if there are tracking requirements outside of the ThingWorx context, check also this Blog post:
The basic Vuforia SDK will allow you to create unique experiences by tracking any object / shape.
For ThingWorx Studio however, those objects are the ThingMarks as they also hold specific object IDs to relate the distinct "instance of an object" with the actual data in the ThingWorx platform.
I hope this helps...