Please make sure that the ticket logo and header image file sizes are not too large since this can cause issues with email deliverability and PDF ticket creation.
The logo image size is not explicitly set in the code which means that you can use any width or height. However, we do recommend that you use a JPG or PNG image that is more or less the size that you want to display the image at e.g. 100 pixels in height and any width. We recommend a JPG image that is 660 pixels in width and any height for the header.