If you race a custom livery it shows as a plain placeholder car here. To show yours:
Only RaceControl links are accepted (they start https://race-control-paints-prod.s3.amazonaws.com/), and the livery must be for the car you are entered with. If you change car or livery during the series, just save the new link.
https://race-control-paints-prod.s3.amazonaws.com/