The Signature Image for your 3D model is its biggest advertisement at TurboSquid. The Signature Image is what customers see on the Search page, where they scan the results to see what looks right for their needs.
By survey, customers are drawn to thumbnails that:
Have a neutral background
Show the entire model clearly
Are free of ancillary items like an environmental background and other 3D objects not included with the model the customer will download
Don't have text, borders, or anything but the model itself
If the customer likes your thumbnail and clicks it to see more, the customer wants to see more images at a high resolution so he/she can inspect the model more closely before making a purchasing decision.
Make it Float
The TurboSquid Search page is set up in such a way that you can make your model appear to "float" on the Search page. Just set your rendering background color to RGB 247,247,247, and the background will blend right in with the Search page. A presentation like this oozes professionalism while showing the customer exactly what you're offering.
Creating Professional Signature Images
Professional Signature Images have these attributes. These are the Signature Image requirements for CheckMate Certification, and are also Best Practices for all models at TurboSquid.
RGB 247,247,247 background to blend in with the search page.
600x600 resolution or above. If over 600x600, must still be square.
Shows the entire model contained in the file, and nothing else. The model can have a slight shadow underneath it.
The entire model and its shadow must fit inside the image without bleeding off the edges of the image.
You should also complement your Signature Image with a Secondary Preview Image, a second rendered thumbnail that shows the model from the same angle and pose, but with a background that enhances the model's realism. This image is required for CheckMate Certification.