Hi Wayne,
You can use CSS to hide the Avatar value. The fieldname "Avatar" would still appear since there's no specific attribute to hide that, but you can at least hide the button to upload the image file and if someone already managed to upload the file, you can prevent the image from appearing using the CSS code "display: none" as described here:
https://www.w3schools.com/css/css_display_visibility.asp
You would just need to debug the page and identify the specific values that are unique to the Avatar, then create your CSS file and upload it to the Look and Feel settings of your LabKey instance:
https://www.labkey.org/Documentation/wiki-page.view?name=customizeLook#resources
Regards,
Jon