The art contest are for testing your creativity and if you are using some image generation apps for it then you don't have a chance to win or deserve to win at all because you are not even working hard for it and just submitting image generated by that app but contest are for original art only.But what I was saying above was there are some members who make 3D art themselves but not on big level.
To win in art contests, you must have good art as well as proof of works. You can not beat so many talented artists if you use automated apps, AI-based art tools. They don't provide you enough high quality arts and you can not show your proof of work too.
Arts made by tools won't match the conditions of art contest too. Furthermore, you can not plagiarise, steal arts of others and submit it in contest then become one of winners.
Art contest participants will inform the manager about that too. Cheaters are not tolerated in art contests by company, manager and participants.