Isn't this lovely? It's an embossed envelope and you can find it at DaWanda. If you aren't familiar with DaWanda, it's an online marketplace similar to Etsy where artists and designers can sell their handmade goods. Unlike Etsy, though, DaWanda is based in Europe.
If you're an Etsy seller, DaWanda is a great place to start if you are trying to break out and reach a larger international customer base.