You can of course add custom cars...
On a more serious note, I strongly suggest they add a community feature that would allow users to add info àla Wikepedia for the cars.
It is just common sense, but it goes beyond that. I thought I would just check the current situation on information available for downloads. I don't see any change there. Because Scalextric don't have the resource to make information available for downloading, having information via the forum would make so much sense. In another forum I belong to I uploaded information on my car (the real sort) to help others. It has been downloaded literally thousands of times.
As images can be uploaded to the forum subject to checking I see no reason why the same could not be done with all support information. However the inclusion of ".pdf" files would be really handy so manuals, instruction sheets and other support information could be included.