Hello,
Any new icons you add will have to be stylized based on the icons class name. You can see an example of one we already did in the Template.CSS files below:
Template.CSS - Line 728
.ion-jet {
display: block;
font-size: 4.3em;
padding-top: 13px;
}
Horizontal Accordion Specific:Template.CSS - Line 2045
.ion-jet.ha {
color: #ffffff;
display: block;
font-size: 4em;
height: 79px;
padding-top: 0;
}