diff --git a/modules/cms/classes/Theme.php b/modules/cms/classes/Theme.php
index 2aace50f9..e6a2f5a00 100644
--- a/modules/cms/classes/Theme.php
+++ b/modules/cms/classes/Theme.php
@@ -396,6 +396,15 @@ class Theme
         return $this->getConfigValue('form', false);
     }
 
+    /**
+     * Returns data specific to this theme
+     * @return Cms\Models\ThemeData
+     */
+    public function getCustomData()
+    {
+        return ThemeData::forTheme($this);
+    }
+
     /**
      * Ensures this theme is registered as a Halcyon them datasource.
      * @return void
@@ -418,7 +427,7 @@ class Theme
     public function __get($name)
     {
         if ($this->hasCustomData()) {
-            $theme = ThemeData::forTheme($this);
+            $theme = $this->getCustomData();
             return $theme->{$name};
         }
 
@@ -433,11 +442,10 @@ class Theme
     public function __isset($key)
     {
         if ($this->hasCustomData()) {
-            $theme = ThemeData::forTheme($this);
-            return isset($theme->{$key});
+            $theme = $this->getCustomData();
+            return $theme->offsetExists($key);
         }
 
         return false;
     }
-
 }
diff --git a/modules/cms/models/ThemeData.php b/modules/cms/models/ThemeData.php
index 4e2e0ba0b..1b02a99e2 100644
--- a/modules/cms/models/ThemeData.php
+++ b/modules/cms/models/ThemeData.php
@@ -3,6 +3,7 @@
 use Lang;
 use Model;
 use Cms\Classes\Theme as CmsTheme;
+use System\Classes\CombineAssets;
 
 /**
  * Customization data used by a theme
@@ -39,6 +40,11 @@ class ThemeData extends Model
      */
     public $rules = [];
 
+    /**
+     * @var array Relations
+     */
+    public $attachOne = [];
+
     /**
      * @var ThemeData Cached array of objects
      */
@@ -56,6 +62,11 @@ class ThemeData extends Model
         $this->setRawAttributes(array_only($this->getAttributes(), $staticAttributes));
     }
 
+    public function afterSave()
+    {
+        CombineAssets::resetCache();
+    }
+
     /**
      * Returns a cached version of this model, based on a Theme object.
      * @param $theme Cms\Classes\Theme
@@ -78,9 +89,16 @@ class ThemeData extends Model
          * Repeater form fields store arrays and must be jsonable.
          */
         foreach ($this->getFormFields() as $id => $field) {
-            if (isset($field['type']) && $field['type'] == 'repeater') {
+            if (!isset($field['type'])) {
+                continue;
+            }
+
+            if ($field['type'] == 'repeater') {
                 $this->jsonable[] = $id;
             }
+            elseif ($field['type'] == 'fileupload') {
+                $this->attachOne[$id] = 'System\Models\File';
+            }
         }
 
         /*
@@ -91,8 +109,9 @@ class ThemeData extends Model
 
     public function beforeValidate()
     {
-        if (!$this->exists)
+        if (!$this->exists) {
             $this->setDefaultValues();
+        }
     }
 
     /**
@@ -119,6 +138,7 @@ class ThemeData extends Model
 
     /**
      * Returns all fields defined for this model, based on form field definitions.
+     * @return array
      */
     public function getFormFields()
     {
@@ -129,4 +149,23 @@ class ThemeData extends Model
             $theme->getConfigValue('form.tabs.fields', []) +
             $theme->getConfigValue('form.secondaryTabs.fields', []);
     }
+
+    /**
+     * Returns variables that should be passed to the asset combiner.
+     * @return array
+     */
+    public function getAssetVariables()
+    {
+        $result = [];
+
+        foreach ($this->getFormFields() as $attribute => $field) {
+            if (!$varName = array_get($field, 'assetVar')) {
+                continue;
+            }
+
+            $result[$varName] = $this->{$attribute};
+        }
+
+        return $result;
+    }
 }
diff --git a/modules/cms/reportwidgets/activetheme/partials/_widget.htm b/modules/cms/reportwidgets/activetheme/partials/_widget.htm
index e3174541a..39c7503a8 100644
--- a/modules/cms/reportwidgets/activetheme/partials/_widget.htm
+++ b/modules/cms/reportwidgets/activetheme/partials/_widget.htm
@@ -24,6 +24,14 @@
             <li>
                 <a href="<?= Backend::url('cms/themes') ?>"><?= e(trans('cms::lang.dashboard.active_theme.manage_themes')) ?></a>
             </li>
+            <?php if ($theme->hasCustomData()): ?>
+                <li>
+                    <a
+                        href="<?= Backend::url('cms/themes/update/'.$theme->getDirName()) ?>">
+                        Customize theme
+                    </a>
+                </li>
+            <?php endif ?>
         </ul>
     <?php else: ?>
         <div class="callout callout-warning">
diff --git a/modules/system/classes/CombineAssets.php b/modules/system/classes/CombineAssets.php
index a748e653f..217a51267 100644
--- a/modules/system/classes/CombineAssets.php
+++ b/modules/system/classes/CombineAssets.php
@@ -1,7 +1,7 @@
 <?php namespace System\Classes;
 
 use App;
-use URL;
+use Url;
 use File;
 use Lang;
 use Cache;
@@ -9,11 +9,13 @@ use Route;
 use Config;
 use Request;
 use Response;
-use Assetic\Asset\AssetCollection;
+use Cms\Classes\Theme;
 use Assetic\Asset\FileAsset;
 use Assetic\Asset\GlobAsset;
 use Assetic\Asset\AssetCache;
+use Assetic\Asset\AssetCollection;
 use Assetic\Cache\FilesystemCache;
+use System\Helpers\Cache as CacheHelper;
 use ApplicationException;
 use DateTime;
 
@@ -317,6 +319,7 @@ class CombineAssets
         $filesSalt = null;
         foreach ($assets as $asset) {
             $filters = $this->getFilters(File::extension($asset)) ?: [];
+            $filters = $this->processFilters($filters);
             $path = File::symbolizePath($asset, null) ?: $this->localPath . $asset;
             $files[] = new FileAsset($path, $filters, public_path());
             $filesSalt .= $this->localPath . $asset;
@@ -346,7 +349,7 @@ class CombineAssets
         $actionExists = Route::getRoutes()->getByAction($combineAction) !== null;
 
         if ($actionExists) {
-            return URL::action($combineAction, [$outputFilename], false);
+            return Url::action($combineAction, [$outputFilename], false);
         }
         else {
             return '/combine/'.$outputFilename;
@@ -465,6 +468,29 @@ class CombineAssets
         }
     }
 
+    /**
+     * Preprocess filters to use standard configuration provided by the system.
+     * @param array $filters
+     * @return array
+     */
+    protected function processFilters($filters)
+    {
+        $theme = Theme::getActiveTheme();
+        if (!$theme->hasCustomData()) {
+            return $filters;
+        }
+
+        $assetVars = $theme->getCustomData()->getAssetVariables();
+
+        foreach ($filters as $filter) {
+            if (method_exists($filter, 'setPresets')) {
+                $filter->setPresets($assetVars);
+            }
+        }
+
+        return $filters;
+    }
+
     //
     // Bundles
     //
@@ -651,17 +677,17 @@ class CombineAssets
      */
     public static function resetCache()
     {
-        if (!Cache::has('combiner.index')) {
-            return;
+        if (Cache::has('combiner.index')) {
+            $index = (array) @unserialize(@base64_decode(Cache::get('combiner.index'))) ?: [];
+
+            foreach ($index as $cacheId) {
+                Cache::forget($cacheId);
+            }
+
+            Cache::forget('combiner.index');
         }
 
-        $index = (array) @unserialize(@base64_decode(Cache::get('combiner.index'))) ?: [];
-
-        foreach ($index as $cacheId) {
-            Cache::forget($cacheId);
-        }
-
-        Cache::forget('combiner.index');
+        CacheHelper::instance()->clearCombiner();
     }
 
     /**