This was 5.75" x 5.5". I knew I was going to give it directly to the person so I didn't bother sizing it to an envelope size.
Tilda is from Magnolia.
The house is from an old SU! set called Happy Haunting.
"PostCard" is from Crafty Secrets: Halloween Vintage Postcard Kit.
"Happy Halloween" is from Rusty Pickle's Boo stamp set.
The bats and pumpkins are from SU!'s Fang-tastic.