How can I draw custom x-axis value in ChartJs by condition?

Question

I need to draw icon 'Attention' instead x-axis value on the ChartJS diagram.

Here is example, how i want to do: https://i.stack.imgur.com/XSsTM.jpg

Is that possible to draw something by conditional in options?

I can change number, return text, but i realy don't know how to draw icon instead value

this.datacollection = {
                labels: [
                    {label: 16, flag: false},
                    {label: 17, flag: false},
                    {label: 18, flag: true},
                    {label: 19, flag: true},
                    {label: 20, flag: false},
                    {label: 21, flag: false},
                ],
                datasets: [
                    {
                        label: 'Something',
                        data: [4, 4, 3, 5, 4, 3, 4, 3, 4, 4, 5, 6, 3, 3],
                        backgroundColor: 'rgba(37,255,63,0.2)',
                        borderColor: 'rgba(37,255,63,1)',
                        borderWidth: 2
                        },
                    {
                        label: 'wrong',
                        data: [2, 2, 3, 5, 3, 6, 4, 2, 2, 5, 5, 6, 7, 7],
                        backgroundColor: 'rgba(255, 99, 132, 0.2)',
                        borderColor: 'rgba(255, 99, 132, 1)',
                        borderWidth: 2
                    }
                ],
            };
...
            this.options = {
                responsive: true,
                maintainAspectRatio: false,
                scales: {
                    xAxes: [{
                        ticks: {
                            userCallback: function (label, index, labels) {
                                if (label.flag) {
                                    return 'here i need an icon'
                                } else {
                                    return label.label;
                                }
                            }
                        }
                    }],
                }