var bilder_switched = {
        "bild-switch_2" : {
                url: 'Bild2.png', 
                imageSize: [722, 154],
                projection: proj,
                imageExtent: proj.getExtent() 
                },
        "bild-switch_1" : {
                url: 'Bild1.png', 
                imageSize: [122, 44],
                projection: proj,
                imageExtent: proj.getExtent()
                },
          ...//weitere Bilder wurden eingefügt     
};

function checkedRadioBtn{
    var allLayers = map.getLayers().getArray()[0];
    map.removeLayer(allLayers);

        for key in (bilder_switched) {
                if(document.getElementById(key).checked){
                        newL = new ol.layer.Image({source: new ol.source.ImageStatic(bilder_switched[key])});
                        map.addLayer(newL);
                }
        }
};