An easy and great way to make an entire room look dressed for halloween is to add black bat cutouts to the wall. Get some back paper, ideally with different finishes, e.g. plain, velvet, glitter, to have more dimension. Then search online for bat clipart. Pick one you like and print it out. Cut out the bat form and then trace it onto the backside of your black paper. Cut the traced bats out of the paper, you can likely do up to 3 at a time. Tape onto your wall with tape you know will come off easily.