frappe/frappe/templates/includes/avatar_macro.html

{% macro avatar(user_id=None, css_style=None, size="avatar-small", full_name=None, image=None) %}
{% set user_info = frappe.utils.get_user_info_for_avatar(user_id) %}
<span class="avatar {{ size }}" title="{{ full_name or user_info.name }}" style="{{ css_style or '' }}">
	{% if image or user_info.image  %}
	<img
		class="avatar-frame standard-image"
		src="{{ image or user_info.image }}"
		title="{{ full_name or user_info.name }}">
	</span>
	{% else %}
	<span
		class="avatar-frame standard-image"
		title="{{ full_name or user_info.name }}">
		{{ frappe.utils.get_abbr(full_name or user_info.name).upper() }}
	</span>
	{% endif %}
</span>
{% endmacro %}