you can create your own images (like the Chips and Stones examples) by using the Target Management System (TMS);
this ix explained in detail in the Dev Guide -> Target Management System -> Create Image Targets
Note that in principle you can upload any image to the TMS, and get back a dataSet that can be used in Vuforia; however, the image will need to contain a sufficient amount of details, as also explained in the DevGuide.
For 3D models, you could create one in Blender and then export it with an "OpenGL export plugin" (you can search the net for such plugins, there exist a few to my knowledge); once exported to OpenGL format, you can replace the "teapot" model with your custom model;
another option is to export the Model (from Blender or other 3D editing tool) to .OBJ format.
Then there exist a simple script that can convert from OBJ to OpenGL.
This is explained step-by-step in detail in:
In general, you need to be familiar with OpenGL programming, otherwise this can be a bit challenging.
An alternative is to use the Vuforia extension for Unity 3D, which allows you to quickly develop stunning 3D applications for bith Android and iOS, and supports various 3D file formats.
I hope this helps.