snapdrop/app/elements/buddy-finder/user-avatar.html

<link rel="import" href="../contact-item/anonymous-contact-behavior.html">
<dom-module id="user-avatar">
    <template>
        <style>
        :host {
            display: block;
            @apply(--layout-vertical);
            @apply(--layout-center);
            width: 120px;
            height: 120px;
        }

        .avatar {
            display: inline-block;
            width: 52px;
            height: 52px;
            border-radius: 50%;
            overflow: hidden;
            background: #ccc;
            @apply(--shadow-elevation-2dp);
        }
        .paper-font-subhead{
        	text-align: center;
        }
        </style>
        <div class="avatar" id="avatar" item-icon></div>
        <div class="paper-font-subhead">{{_displayName}}</div>
    </template>
    <script>
    'use strict';
    Polymer({
        is: 'user-avatar',
        behaviors:[Chat.AnonymousContactBehavior],
        observers:['_computeBackgroundImg(contact.*)'],
        _computeBackgroundImg:function(){
            console.log('avatar changed');
            var avatar = this.anonymousAccount(this.contact).avatar;
            var style = this.$.avatar.style;
            style.backgroundImage='url('+avatar.url+')';
            style.backgroundPosition=avatar.left+'px '+avatar.top+'px';
        }
    });
    </script>
</dom-module>