Please try adding this script to your select question:
<style>
#[% QuestionName() %]_div .input_cell {
display: none;
}
.selectedImg {
border: 1px solid blue;
}
</style>
<script>
$(document).ready(SSI_CustomGraphicalCheckbox);
function SSI_CustomGraphicalCheckbox() {
$('input[name="hid_list_[% QuestionName() %]"]').val().split(',').forEach(function(item){
var id = '[% QuestionName() %]_' + item;
$('#' + id).closest('.clickable').find('img').toggleClass('selectedImg', SSI_GetValue(id) == 1);
})
}
</script>
Line 7 can be updated with the visual changes you want for selected images.