At first, designing a wreath seems simple but I've found it to be somewhat challenging to make them look just right. Keeping it simple is the way to go. Start with an inexpensive grapevine wreath from the craft store, spray paint it black, and, if desired, stick a scary object in the middle (a raven, spider, severed hand). Done! Last year, The Queen of Halloween gave me the courage to attempt my own wreath (the one with the crow below) and let's just say my results were graded as "E" for effort. I tried again this year with my toxic spider motif, and had slightly better results. Maybe the sophisticated crafting required for "wreathery" is not my forte.
For some real inspiration on more thoughtfully designed wreaths, take a look at some of these wicked wreaths that I've found online.
Howling Moon Wreath from Chic-Adee Shop
Toothpick Wreath by The Magic of Ordinary Things
Skeleton Wreath by Ready, Set, Craft!
Snake Wreath by My Momma Told Me
Black Twig Wreath as seen on Snappy Pixels