In addition to the previous threads on appearance customization that @RockmanX linked to, have a look around for discussions on the broader issue of a set main character rather than one that can be shaped by the player. Like this:
Plenty of people don’t care. Plenty of others care a lot, and of those who do, the majority want to be able to self-insert or otherwise customize their protagonist. Picking name, gender, and orientation in particular is a must-have for a significant chunk of the playerbase.
If you go for a fixed MC and make the most of that opportunity by writing a rich and interesting protagonist, you’ve got a good chance of finding an enthusiastic audience – and a near-certainty of getting some online reviews saying “why didn’t he write a novel?” and “no character customization, 1 star.”
For a head start on how to code the choice of gender, this thread has some links: