Use custom mascot on static share page

app/helpers/mascot_helper.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module MascotHelper
+  def mascot_url
+    full_asset_url(instance_presenter.mascot&.file&.url || asset_pack_path('media/images/elephant_ui_plane.svg'))
+  end
+
+  private
+
+  def instance_presenter
+    @instance_presenter ||= InstancePresenter.new
+  end
+end

app/javascript/styles/mastodon/modal.scss

@@ -12,10 +12,19 @@
   flex-direction: column;
   justify-content: flex-end;
 
-  > * {
+  > div {
     flex: 1;
     max-height: 235px;
-    background: url('../images/elephant_ui_plane.svg') no-repeat left bottom / contain;
+    position: relative;
+
+    img {
+      max-height: 100%;
+      max-width: 100%;
+      height: 100%;
+      position: absolute;
+      bottom: 0;
+      left: 0;
+    }
   }
 }
 

app/views/layouts/modal.html.haml

@@ -14,5 +14,6 @@
   .container-alt= yield
   .modal-layout__mastodon
     %div
+      %img{alt:'', draggable:'false', src:"#{mascot_url}"}
 
 = render template: 'layouts/application'