Leaflet: impossible to remove specific image layer - leaflet

Question

Below are three functions that I use to respectively create a map, add an IMG-layer and remove an IMG-layer. Problem is that when I add an IMG-layer and then want to remove it before adding a new (different) IMG-layer......the removal is not taking place.
The IMG-layers that I use are simple URLs to png's.
So subsequently:
loadMap();
SetLayer("2018_10_13_16_15.png");
RemoveLayer("2018_10_13_16_15.png");
SetLayer("2018_10_13_16_30.png");
Then "2018_10_13_16_15.png" is not removed.
What am I doing wrong??
var map = L.map('map');
var imageBounds = [[50.520, 0.813], [54.295, 10.996]];
function loadMap(){
map.createPane('labels');
var positron = L.tileLayer('http://{s}.basemaps.cartocdn.com/light_nolabels/{z}/{x}/{y}.png', {
attribution: cartodbAttribution
}).addTo(map);
var positronLabels = L.tileLayer('http://{s}.basemaps.cartocdn.com/light_only_labels/{z}/{x}/{y}.png', {
attribution: cartodbAttribution,
pane: 'labels'
}).addTo(map);
map.setView({lat: 52.5, lng: 5.2}, 6.5);
isMap = true; //map is loaded
}
function SetLayer(url) {
IMGLayer = L.imageOverlay(url, imageBounds);
IMGLayer.addTo(map);
}
function RemoveLayer(url) {
IMGLayer = L.imageOverlay(url, imageBounds);
IMGLayer.removeFrom(map);
}