Hey,
The list is created using the following structure by default:
<ul class="asl-screenshot-list">
<li class="asl-app-screenshot"><img src="LINK" alt="App Screenshot" width="480"/></li>
</ul>
You can use the asl-screenshot-list and asl-app-screenshot classes in your theme’s style.css to customize the look. To remove the bullet points, try:
ul.asl-screenshot-list { list-style-type:none; }
To answer your second question:
Unfortunately, the Google Play store doesn’t have a convenient Search API like Apple does, so I don’t have anything for that right now. I am still looking into options for putting a plugin together for that at some point.