md-avatar.html

<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../jquery-extensions/jquery-extensions.html">
<style>
    md-avatar{
        position:relative;
    }
</style>
<dom-module id="md-avatar">
    <template>
        <img class="avatar">
        <content></content>
    </template>
</dom-module>
<script>

    Polymer({

        is: 'md-avatar',

        properties: {
            defaultUrl:{
                type:String,
                value:null
            },
            src: {
                type: String,
                value: null
            },
            dataClass: {
                type: String,
                value: null
            }
        },

        ready: function () {
            var src=this.src;
            var defaultUrl=this.defaultUrl;
            var img=$(this).find('.avatar');
            if(src)img.attr('src',src);
            else if(defaultUrl) img.attr('src',defaultUrl);
            if(this.dataClass) img.addClass(this.dataClass);
        }
    });

</script>