CET Designer supports the import of 3D models from SketchUp. This allows you to choose from a huge library of objects of all sorts. Add these objects to your drawing to achieve a more realistic impression.
The SketchUp Extension is available on the Marketplace.
After downloading and installing the Extension, you'll have a new SketchUp component tab in CET Designer. Here, models can either be imported from file (i.e. models that you have downloaded to a location of your choice), or imported from the 3D Warehouse.