This worked for me.
using CSS to modify the inner span in the button tag of each option, removing radius and assigning a brackground image
the options keep the same order, and that is why the attribute selector worked for me
.alert-radio-icon{
border-radius: 0 !important;
border: none !important;
height: 40px !important;
width: 40px !important;
background-size: 40px 40px !important;
background-repeat: no-repeat ;
}
[id^="alert-input-"][id$="-0"] .alert-radio-icon{
background-image: url("../assets/images/menu/flag_ni.png") !important;
}
[id^="alert-input-"][id$="-1"] .alert-radio-icon{
background-image: url("../assets/images/menu/flag_gt.png") !important;
}
.alert-radio-inner{
background-color: transparent !important;
}