I really like the object models from The Stanford 3D Scanning Repository. Unfortunately I couldn't get the permission to include them as build-in objects in Shaderific, since they are not licensed for commercial purposes.
But if you want to use them with Shaderific, you can import the objects yourself. For any other than private use, please make sure to read the guidelines for proper acknowledgment and appropriate use of the models at The Stanford 3D Scanning Repository.
The three object models from the repository I like the most are the Stanford Bunny, the Happy Buddha and the Dragon. Alejo Grigera (a.k.a. Mr Bluesummers) has converted these objects from the original Standford .ply files to .obj format and you can download them at his website.
The numbers above are for the converted objects in .obj format.
You can see some example images using the Stanford Bunny and read about the history of the model at Greg Turk's website.