When you upload the files of your model, you should include a picture that will show to the other users how your model looks like. Even if you are not a render master, there are several tricks you can use to save an imagine from your work.
Most of the CAD systems provide a command to "save as an image" the current view. Usually, this command is available in the "save as" menu or in the option menu
Answered with a tutorial: https://grabcad.com/tutorials/tutorial-how-to-easily-produce-a-picture-to-upload-with-your-model
I hope these tutorials help users to upload their models more properly.