Been intrigued by this so I started making faces for the better newgens in my Wimbledon save -posting some of the results and the query for people that want to try and do what I did.
I used "ultra realistic 8k, (ethnicity) (nationality) footballer, (hair), (facial hair), (color) shirt with (color) collar, portrait --upbeta" as the prompt and it came up with these:
some results are unusable and a little ridiculous (half blue, half yellow hair, dreadlocks growing out of ears, etc.) but after some photoshop tuning they look awesome in-game (I'll update the post with some in-game shots after work)