General How do you make a custom background for previews or do you have a link to a good one

[ibanezcollector]

Ok so I got a lot of cars, and I want to update my previews to something a tad nicer looking but cant seem to find a good preview mod everything is for custom showroom or a track and I want to batch a lot at one time with just using the standard update preview section.
So my question is how do you make a custom preview background to be used in the update preview section or do you have a good one that you personally like?