You can use this to show the avatar of the OP in Mobile view:
<script type='text/x-handlebars' data-template-name='mobile/list/topic-list-item.raw'>
<td>
{{~#unless expandPinned}}
<div class='pull-left'>
<a href="/users/{{topic.creator.username}}">{{avatar topic.creator imageSize="large"}}</a>
</div>
<div class='right'>
{{else}}
<div>
{{/unless~}}
<div class='main-link'>
{{raw "topic-status" topic=topic}}
{{topic-link topic}}
{{#if topic.featured_link}}
{{topic-featured-link topic}}
{{/if}}
{{#if topic.unseen}}
<span class="badge-notification new-topic"></span>
{{/if}}
{{~#if expandPinned}}
{{raw "list/topic-excerpt" topic=topic}}
{{/if~}}
</div>
<div class='pull-right'>
{{raw "list/post-count-or-badges" topic=topic postBadgesEnabled=showTopicPostBadges}}
</div>
<div class="topic-item-stats clearfix">
{{#unless hideCategory}}
<div class='category'>
{{category-link topic.category}}
</div>
{{/unless}}
{{discourse-tags topic mode="list"}}
<div class="pull-right">
<div class='num activity last'>
<span class="age activity" title="{{topic.bumpedAtTitle}}"><a href="{{topic.lastPostUrl}}">{{format-date topic.bumpedAt format="tiny" noTitle="true"}}</a></span>
</div>
</div>
<div class="clearfix"></div>
</div>
</div>
</td>
</script>