Edit your index.html file location in the public folder. Copy your image to same location as index.html in public folder.
And then replace the part of the contents of index.html containing <div id="root"> </div>
tags to the below given html code.
<div id="root"> <img src="logo-dark300w.png" alt="Spideren" style="vertical-align: middle; position: absolute;
top: 50%;
left: 50%;
margin-top: -100px; /* Half the height */
margin-left: -250px; /* Half the width */" /> </div>
Logo will now appear in the middle of the page during the loading process. And will then be replaced after a few seconds by React.