--- a/browser/components/customizableui/CustomizableWidgets.jsm
+++ b/browser/components/customizableui/CustomizableWidgets.jsm
@@ -1141,16 +1141,17 @@ if (Services.prefs.getBoolPref("privacy.
       ContextualIdentityService.getIdentities().forEach(identity => {
         let bundle = doc.getElementById("bundle_browser");
         let label = bundle.getString(identity.label);
 
         let item = doc.createElementNS(kNSXUL, "toolbarbutton");
         item.setAttribute("label", label);
         item.setAttribute("usercontextid", identity.userContextId);
         item.setAttribute("class", "subviewbutton");
+        item.setAttribute("image", identity.icon);
 
         fragment.appendChild(item);
       });
 
       items.appendChild(fragment);
     }
   });
 }

--- a/browser/themes/shared/customizableui/panelUIOverlay.inc.css
+++ b/browser/themes/shared/customizableui/panelUIOverlay.inc.css
@@ -1445,16 +1445,21 @@ toolbaritem[overflowedItem=true],
   -moz-appearance: none;
   margin-inline-end: 3px;
 }
 
 menuitem[checked="true"].subviewbutton > .menu-iconic-left {
   visibility: hidden;
 }
 
+#PanelUI-containersItems > .subviewbutton > .toolbarbutton-icon {
+  width: 16px;
+  height: 16px;
+}
+
 .panel-mainview[panelid=customizationui-widget-panel],
 #customizationui-widget-multiview > .panel-viewcontainer,
 #customizationui-widget-multiview > .panel-viewcontainer > .panel-viewstack,
 #PanelUI-panicView > .panel-subview-body,
 #PanelUI-panicView {
   overflow: visible;
 }