saw how checkbox images were called in css variables, so updated pageImgURL variable.

public/sass/_variables.dark.scss

@@ -50,7 +50,7 @@ $critical:              #ed2e18;
 // -------------------------
 $body-bg:  			   rgb(20,20,20);
 $page-bg:  			   $dark-2;
-$page-img-bg: 		   url('../img/angle_gradient_rev.png');
+$pageImageUrl: 		   '../img/angle_gradient_rev.png';
 $body-color:   		   $gray-4;
 $text-color:   	       $gray-4;
 

public/sass/_variables.light.scss

@@ -56,7 +56,7 @@ $critical:              #EC2128;
 
 $body-bg:  		$white;
 $page-bg:  		$white;
-$page-img-bg: 	url('../img/angle_gradient_light_rev.png');
+$pageImageUrl: 	'../img/angle_gradient_light_rev.png';
 $body-color:    $gray-1;
 $text-color:    $gray-1;
 

public/sass/layout/_page.scss

@@ -20,7 +20,7 @@
 
 .page-container {
   background-color: $page-bg;
-  background-image: $page-img-bg; /* this is an experiment */
+  background-image: url($pageImageUrl); /* this is an experiment */
   background-position: left;
   background-size: 60%;
   background-repeat: no-repeat;

public/sass/pages/_login.scss

 .login-container {
-  background-image: $page-img-bg; /* this is an experiment */
+  background-image: url($pageImageUrl); /* this is an experiment */
   background-position: left;
   background-size: 60%;
   background-repeat: no-repeat;