What about giving the 'mascots' names (if they don't already have them), and having something like 'Choose your mascot: Bob or Sally' (or whatever). Unless it's because you are using the info for analytics, in which case it could be an additional question alongside 'Male / Female / Prefer not to say'. This way you can continue with the binary level avatar approach, but also collect optional gender data for analysis. Just a thought.
What about giving the 'mascots' names (if they don't already have them), and having something like 'Choose your mascot: Bob or Sally' (or whatever). Unless it's because you are using the info for analytics, in which case it could be an additional question alongside 'Male / Female / Prefer not to say'. This way you can continue with the binary level avatar approach, but also collect optional gender data for analysis. Just a thought.