Add gold leafing to the house key. You can do this by using a brush to coat the key in glue. Allow to get tacky, then wrap the key in gold leaf. Use a second brush to brush away any excess.
You may need to go over certain areas of the key again, as gold leaf can be quite flaky.
Create a bow from a pipe cleaner or small ribbon.
Use yarn to tie the key and bow to the mini wreath, leaving a loop on top to hang from a Christmas tree.