You can google haunted Halloween silhouettes.
Using paint create a base using yellow, orange, red or purple. Make sure to have the moon in the background another colour. You can use multiple colours for your sky and background.
While you are waiting for your Halloween background to dry start cutting out a haunted Halloween castle and silhouette using black construction paper. Use pencil and lots of details.
To get the window effect you can cut out holes for the windows and paint them in again using the background colour. The more detail the better.
You can add bats etc. Before you glue your construction paper on your picture needs to be dry. The spookier the better!!! Good luck ghouls and goblins.