The log image url needs to be something of this nature:
https://yourweb/picture.jpg If the file itself is not a .png .jpg or .gif then the logo image will not display properly.
Note:
Logo Image URL - Choose an image with a maximum size of 190 pixels wide by 60 pixels high. The image will appear at the top of the order summary. We recommend providing an image that's stored on a secure (https) server.
Header Image URL - Please specify an image that I
s a maximum size of 750 pixels wide by 90 pixels high. Larger images will be cut to this size. The image you choose will appear at the top left of the payment page. We recommend providing an image only if it is stored on a secure (https) server.
In the button coding add this line for logo or header display"
<input type="hidden" name="image_url" value="
https://yourwebsite.com/assets/cart_images/logo_paypal.png" />
