Can a model or image which are outside the unity 3d project

I a noob in Unity3D.

I tried using AssetBundle but for that to work I need to build the model or image into a Unity3D Project file using build asset pipeline. Which can then be imported into the existing project executable at runtime.

I wanted to know can I import a model / image at runtime from a particular folder on a system. Without converting the model / image into a unity3d project file?

I want something like a raw import of model / image at runtime which then be converted to unity3d required format using unity3d function at runtime.

For images, use the WWW class (works for PNG and JPG). For models, you will have to write an importer or use an existing one, such as ObjReader.