Add background image for icons

assets/stylesheets/editor-3/_color-bar.scss

@@ -191,3 +191,13 @@
 .CustomList-item--invert:hover .ColorBar-invertLink {
   opacity: 1;
 }
+
+.IconContainer {
+  display: flex;
+  border-radius: 2px;
+  background-image:
+    linear-gradient(45deg, rgba(#000, 0.08) 25%, transparent 25%, transparent 75%, rgba(#000, 0.08) 75%, rgba(#000, 0.08)),
+    linear-gradient(45deg, rgba(#000, 0.08) 25%, transparent 25%, transparent 75%, rgba(#000, 0.08) 75%, rgba(#000, 0.08));
+  background-position: 0 0, 4px 4px;
+  background-size: 8px 8px;
+}

lib/assets/javascripts/builder/components/form-components/editors/fill-color/inputs/input-image.tpl

@@ -1,6 +1,6 @@
 <% if (image && !isCustomMarker) { %>
 <button type="button" class="Editor-fillImage <% if (help) { %> js-help<% } %>" <% if (help) { %> data-tooltip="<%- help %>"<% } %>>
-  <div class="js-image-container"></div>
+  <div class="IconContainer js-image-container"></div>
 </button>
 <% } %>