If you're doing it based on user groups, you could just use conditionals: https://xenforo.com/community/resources/conditional-statements-for-xenforo-2.5795/Did you find a way to achieve this?
I would like to have the same feature associated with groups, so that each group could have its avatar below the user's avatar.
<xf:macro name="user_info"
    arg-user="!"
    arg-fallbackName="">
    <section itemscope itemtype="https://schema.org/Person" class="message-user">
        <div class="message-avatar {{ ($xf.options.showMessageOnlineStatus && $user && $user.isOnline()) ? 'message-avatar--online' : '' }}">
            <div class="message-avatar-wrapper">
                <xf:avatar user="$user" size="m" defaultname="{$fallbackName}" itemprop="image" />
                <xf:if is="$xf.options.showMessageOnlineStatus && $user && $user.isOnline()">
                    <span class="message-avatar-online" tabindex="0" data-xf-init="tooltip" data-trigger="auto" title="{{ phrase('online_now')|for_attr }}"></span>
                </xf:if>
            </div>
        </div>
        <div class="message-userDetails">
            <h4 class="message-name"><xf:username user="$user" rich="true" defaultname="{$fallbackName}" itemprop="name" /></h4>
            <xf:usertitle user="$user" tag="h5" class="message-userTitle" banner="true" itemprop="jobTitle" />
            <xf:userbanners user="$user" tag="div" class="message-userBanner" itemprop="jobTitle" />
        </div>
        <xf:if is="$user.user_id">
            <xf:set var="$extras" value="{{ property('messageUserElements') }}" />
            <xf:if contentcheck="true">
                <div class="message-userExtras">
                <xf:contentcheck>
                    <xf:if is="$extras.register_date">
                        <dl class="pairs pairs--justified">
                            <dt>{{ phrase('joined') }}</dt>
                            <dd>{{ date($user.register_date) }}</dd>
                        </dl>
                    </xf:if>
                    <xf:if is="$extras.message_count">
                        <dl class="pairs pairs--justified">
                            <dt>{{ phrase('messages') }}</dt>
                            <dd>{$user.message_count|number}</dd>
                        </dl>
                    </xf:if>
                    <xf:if is="$extras.reaction_score">
                        <dl class="pairs pairs--justified">
                            <dt>{{ phrase('reaction_score') }}</dt>
                            <dd>{$user.reaction_score|number}</dd>
                        </dl>
                    </xf:if>
                    <xf:if is="$extras.trophy_points && $xf.options.enableTrophies">
                        <dl class="pairs pairs--justified">
                            <dt>{{ phrase('points') }}</dt>
                            <dd>{$user.trophy_points|number}</dd>
                        </dl>
                    </xf:if>
                    <xf:if is="$extras.age && $user.Profile.age">
                        <dl class="pairs pairs--justified">
                            <dt>{{ phrase('age') }}</dt>
                            <dd>{$user.Profile.age}</dd>
                        </dl>
                    </xf:if>
                    <xf:if is="$extras.location && $user.Profile.location">
                        <dl class="pairs pairs--justified">
                            <dt>{{ phrase('location') }}</dt>
                            <dd>
                                <xf:if is="$xf.options.geoLocationUrl">
                                    <a href="{{ link('misc/location-info', '', {'location': $user.Profile.location}) }}" rel="nofollow noreferrer" target="_blank" class="u-concealed">{$user.Profile.location}</a>
                                <xf:else />
                                    {$user.Profile.location}
                                </xf:if>
                            </dd>
                        </dl>
                    </xf:if>
                    <xf:if is="$extras.website && $user.Profile.website">
                        <dl class="pairs pairs--justified">
                            <dt>{{ phrase('website') }}</dt>
                            <dd><a href="{$user.Profile.website}" rel="nofollow" target="_blank">{$user.Profile.website|url('host', phrase('visit_site'))}</a></dd>
                        </dl>
                    </xf:if>
                    <xf:if is="$extras.custom_fields">
                        <xf:macro template="custom_fields_macros" name="custom_fields_values"
                            arg-type="users"
                            arg-group="personal"
                            arg-set="{$user.Profile.custom_fields}"
                            arg-additionalFilters="{{ ['message'] }}"
                            arg-valueClass="pairs pairs--justified" />
                        <xf:if is="$user.canViewIdentities()">
                            <xf:macro template="custom_fields_macros" name="custom_fields_view"
                                arg-type="users"
                                arg-group="contact"
                                arg-set="{$user.Profile.custom_fields}"
                                arg-additionalFilters="{{ ['message'] }}"
                                arg-valueClass="pairs pairs--justified" />
                        </xf:if>
                    </xf:if>
                </xf:contentcheck>
                </div>
            </xf:if>
        </xf:if>
        <span class="message-userArrow"></span>
    </section>
</xf:macro><xf:if is="{$user.Profile.custom_fields.userlogo}">
<div><img src="{$user.Profile.custom_fields.userlogo}" /></div>
</xf:if>                <xf:avatar user="$user" size="m" defaultname="{$fallbackName}" itemprop="image" />
                <xf:if is="$xf.options.showMessageOnlineStatus && $user && $user.isOnline()">
                    <span class="message-avatar-online" tabindex="0" data-xf-init="tooltip" data-trigger="auto" title="{{ phrase('online_now')|for_attr }}"></span>
                </xf:if>
<xf:if is="{$user.Profile.custom_fields.userlogo}">
<div><img src="{$user.Profile.custom_fields.userlogo}" /></div>
</xf:if><xf:if is="{$user.isMemberOf(3)}">
<div><img src="https://www.yourwebsite.com/images/usertitles/admin-title-image.png" /></div>
<xf:elseif is="{$user.isMemberOf(4)}" />
<div><img src="https://www.yourwebsite.com/images/usertitles/mod-title-image.png" /></div>
<xf:elseif is="{$user.isMemberOf(5)}" />
<div><img src="https://www.yourwebsite.com/images/usertitles/member-title-image.png" /></div>
<xf:else />
</xf:if><div><center><img src="https://www.yourwebsite.com/images/usertitles/admin-title-image.png" /></center></div>We use essential cookies to make this site work, and optional cookies to enhance your experience.