Autodesk Infastructure Modeler has many very cool features and can present quite the "wow" factor when showing clients and collegues what it can do. Just have a look at this video that was shared on Civil 3D's Facebook page. Given the realistic detail that can be achieved, you want to make sure everything is being imported properly.
In this case we will talk about SketchUp (SKP) models and having actual photos of the real buildings applied to said models. If after tying to import these models into Infastructure Modeler you find that you are missing the materials (photos) it may be due to the fact that Infastructure Modeler cannot "see" those materials.
If you are exporting to the DAE file format, you will get the DAE file and a folder with the same name. The folder contains the JPG required for the model textures. To resolve this try moving the DAE file into the folder that contains the JPG. That way, when the DAE is imported into Infastructure Modeler, the textures are found and used.