So what exactly counts against a custom gamerpic?

Its not really worth it. I'll just use the same picture. I have already trimmed it to be at least rated PG-13. I mean its fortnite for heavens sake.

The picture needs to rated E for everyone.If you use the same picture,even trimmed down,you'll more than likely get another suspension but longer this time & possibly lose the option to use custom gamerpics at all.Is it really worth the risk?

If it is reported then a case is created for the Enforcement Team to look at and then they decide if it follows the Code of Conduct.

If your pic was accepted in the first pace then it could have been reported and taken down, if there is a valid argment against the picture enforcement will take it down.

Did you have any other images uploaded, even momentarily?

From the Enforcement website:

What happens if I upload inappropriate custom images?

If you upload an inappropriate custom image it may be removed and replaced with the most recent Microsoft-created image that you used, and you will be prevented from uploading any additional imagery for a specific period (typically 24 hours). Repeated violations
or especially inappropriate images may result in lengthier suspensions.

Keep in mind that once you’ve uploaded an image, even if it was shown only briefly or was subsequently changed, it may get reviewed and the account may still be subject to enforcement action.

https://enforcement.xbox.com/en-US/home/staysafe#topic13

Yea it had none of these. Unless someone takes offence to the female body. But that would just be sexist

It may have been

"Use someone’s intellectual property in an unauthorised way"