Introduction
If you want to replace the default CSS spinner with a custom image in Gravity Forms, add the following CSS code to your theme’s stylesheet or custom CSS area.
.entry-content .gform-theme--foundation .gform-loader {
border: none;
animation: none;
transform: none;
width: 20px;
height: 20px;
display: inline-block;
background: url('YOUR URL HERE');
background-size: contain;
background-repeat: no-repeat;
background-position: center;
}
Placement
You can add your Custom CSS to the Customizer (Appearance → Customize) or your child theme stylesheet.
See also: Where to Put your Custom CSS.