Is it possible to change the theme structure in blogger

Question

You see that green space I want to replace it with picture I want to put a picture in place of that welcome in my blog's landing page.Here is the template's html for the widget featured post one. Are there changes that I can make in the c*de to attain the picture in place of that welcome in the green space.

<b:widget cond='data:view.isHomepage' id='FeaturedPost1' locked='true' 
   title='' type='FeaturedPost' visible='true'>
                  <b:widget-settings>
                    <b:widget-setting name='showSnippet'>true</b:widget- 
    setting>
                    <b:widget-setting name='showPostTitle'>true</b:widget- 
    setting>
                    <b:widget-setting 
   name='postId'>3725292005206811617</b:widget-setting>
                    <b:widget-setting name='showFirstImage'>true</b:widget- 
   setting>
                    <b:widget-setting 
   name='useMostRecentPost'>false</b:widget-setting>
                  </b:widget-settings>
                  <b:includable id='main' var='this'>
        <b:include name='widget-title'/>
   <div class='widget-content'>
 <b:include name='snippetedPosts'/>
 </div>
 </b:includable>
                  <b:includable id='commentsLink'>
      <a class='comment-link flat-button ripple' 
 expr:href='data:post.commentsUrl' 
 expr:onclick='data:post.commentsUrlOnclick'>
        <b:if cond='data:post.numberOfComments &gt; 0'>
          <b:message name='messages.numberOfComments'>
            <b:param expr:value='data:post.numberOfComments' 
 name='numComments'/>
          </b:message>
        <b:else/>
          <data:messages.postAComment/>
        </b:if>
      </a>
    </b:includable>

Answer 1

First, try including an image in your post. There is a part of your code that uses the first image of every post as the thumbnail, or else, uses a blank page or any other default thumbnail. In your case, a green background box is used instead.

Include the image you want into your post. You can also change the default thumbnail, but I don't know exactly how your code is. You could look for it or make your code available.