Custom CSS for a bordered box image choices based on first example at https://jetsloth.com/gravity-forms-image-choices/

image-choices-border-box-example.css

.gform_wrapper .gfield.image-choices-field .image-choices-choice,
.image-choices-field .image-choices-choice {
	padding: 5% 15px 6%!important;
    border-radius: 9px;
    box-shadow: inset 4px 4px 10px transparent, 4px 4px 10px transparent;
    border: 3px solid rgba(0, 0, 0, 0);
    width: 30%;
    margin-left: 1% !important;
    margin-right: 1% !important;
    background-color: transparent;
}

.gform_wrapper .gfield.image-choices-field .image-choices-choice label,
.image-choices-field .image-choices-choice label {
	border: 0!important;
    padding: 0 !important;
    display: block;
}

.gform_wrapper .gfield.image-choices-field .image-choices-choice .image-choices-choice-image-wrap,
.image-choices-field .image-choices-choice .image-choices-choice-image-wrap {
	background-color: transparent;
	border: none;
    border-radius: 50%;
    background-size: cover;
    width: 100%;
    height: auto;
    padding-bottom: 100%;
}

.gform_wrapper .gfield.image-choices-field .image-choices-choice-text,
.image-choices-field .image-choices-choice-text {
	font-size: 18px;
    color: #000;
    padding-top: 20px;
}

.gform_wrapper .gfield.image-choices-field .image-choices-choice.image-choices-choice-selected,
.image-choices-field .image-choices-choice.image-choices-choice-selected {
	border-color: #000;
    box-shadow: inset 4px 4px 10px rgba(0, 0, 0, 0.2), 4px 4px 10px rgba(0, 0, 0, 0.2);
}