I used the graphic set Get a Job (you could also use the SVG if you wanted the parts already separated).
I mirrored the tank to turn it around, then added a shadow of a darker color to give it depth. I shadowed again in white, which I used as the base for the shaped card. The font for "Tanks" is Bookworm (free here), this was shadowed just enough that the shadow touched and connected the word. I cut these out from Silhouette Studio as Print-n-Cut, using the registration marks. In order to fit the card on the page, I rotated it. The inside is left blank for your own sentiment.
The envelope is my own design, you can download it here. It was designed and printed from MTC.