fixes #6626

src/meta/themes.js

@@ -104,9 +104,9 @@ Themes.get = function (callback) {
 						// Minor adjustments for API output
 						configObj.type = 'local';
 						if (configObj.screenshot) {
-							configObj.screenshot_url = 'css/previews/' + encodeURIComponent(configObj.id);
+							configObj.screenshot_url = nconf.get('relative_path') + '/css/previews/' + encodeURIComponent(configObj.id);
 						} else {
-							configObj.screenshot_url = 'assets/images/themes/default.png';
+							configObj.screenshot_url = nconf.get('relative_path') + '/assets/images/themes/default.png';
 						}
 						next(null, configObj);
 					} catch (err) {

src/views/admin/partials/theme_list.tpl

@@ -1,7 +1,7 @@
 <!-- BEGIN themes -->
 <div class="col-lg-4 col-md-6 col-sm-12 col-xs-12" data-type="{themes.type}" data-theme="{themes.id}"<!-- IF themes.css --> data-css="{themes.css}"<!-- ENDIF themes.css -->>
 	<div class="theme-card mdl-card mdl-shadow--2dp">
-		<div class="mdl-card__title mdl-card--expand" style="background-image: url('{relative_path}/{themes.screenshot_url}');"></div>
+		<div class="mdl-card__title mdl-card--expand" style="background-image: url('{themes.screenshot_url}');"></div>
 		<div class="mdl-card__supporting-text">
 			<h2 class="mdl-card__title-text">{themes.name}</h2>
 			<p>