Here you go (shout out to sama74 from SP who helped get this going)
- Upload this image to your Staff > Assets topic
- Go to Admin > Customize > CSS
#current-user div {
position: relative;
}
#current-user div::after {
position: absolute;
content: '';
display: block;
top:-16px;
left: -8px;
width: 45px;
height: 45px;
/* UPDATE THE URL BELOW */
background: url(url_of_christmas_hat_asset) no-repeat center;
background-size: contain;
}
Last but not least, make sure the customization is saved and enabled.