How To Change The Widget Posts with Thumbnails Image Size

By default the Post with Thumbnails widget uses the thumbnail size which is defined in WordPress at Settings > Media. You can select another size if you want though when you edit the widget:

noir-widget-posts-with-thumbnail

However, in order for the widget to be designed in a way that the title and date do not ever flow under the image the theme must add CSS to give the thumbnail a fixed size. You would have to also add custom CSS to your site to alter this design (custom CSS can be added at Appearance > Custom CSS). Example:

<pre>
.widget-recent-list .wpex-thumbnail {
width: 70px; /* change this value */
height: 70px; /* change this value */
}
/* you min-height value should be equal to your thumbnail height plus 15px */
.widget-recent-list li {
min-height: 85px;
}

</pre>