A very important concept when thinking about images to import into a 3D program is the positive and negative space of the image. Which part is the solid and to be printed and what is the negative space or air?
Lots of things you see around you use tricks to make sure that all of the positive space is connected so that they stay attached to each other. IN this case all the letters are attached to the logo itself making it possible to have the full logo as one object.
Another trick is to modify the object to connect objects that would otherwise fall out object.
Things you encounter every day that make use of very simple representations of positive and negative space making them ideal candidates for tracing and bringing in to a 3D program to modify are icons, logos and symbols. As seen in this icon it is a simplified representation of an object that can be easily transformed.
Iconic logos are intentionally made to be easily readable as an outline due to all of the ways that it will be used for branding.
Symbols are also a great source of simplified and ready to use shapes for importing. Using icon logo or symbol in your image searches will help you quickly find great resources for importing into a 3D program and customizing objects or as a starting point template for building objects.