I make my own mailing labels when I need them. Here's an idea for you.
After your wedding is over and it's time to send out the thank you notes, customize your mailing labels.
I created the design in my Pazzles Pro 2010 software. The image is from the Pazzles gallery. I broke the image apart in MTC so I could add some color. The original image is black and white. I added the text while I was inside the Pazzles software and added a right side border.
For the first image, I used Avery 5354 template in MS Word. I don't buy the store labels anymore, I just print the labels on paper, cut to size and adhere to my envelope and or box. I adhere the labels differently based on the packaging. The best way I have found is to use the wide clear packing tape to cover my label - leaving about a 1/4" on all sides to adhere to my envelope. On a larger box I just completely cover the label while sealing the box.
This image is of Avery 5524 template in MS Word, which is a larger mailing label.
If you use adhesive backed paper, you could easily print these onto that paper and cut them out to customize your labels even more.
Here's a mailing label using one of my paper dolls (fictitious company name).