I purchased the thank you cards from Michaels, I love the damask pattern, it matches the banner on my Etsy shop. The pack has 40 cards, 40 envelops and 40 little thank you oval like parts that you can put if you like.
I had a stamp made with my logo and I purchased black, purple and pink ink to match the logo colors. The good thing about the stamp is that I can use it for anything I have put it on bags, boxes and have even made tags with it too.
It's a little bit of work because I have to go slowly and be careful with the colors on the stamp but I think it's worth it.
The card opens up and inside I hand write my thank you note.