Here is a sample and instructions of a card that I'm made for a client. It shows how to use a regular sized photo (4x6) and turn it into a landscape photo. The end result is a 4x8 landscape card that easily slips into a #10 envelope. You can also do the same process with portraits 6x4's. Long card instead of wide. Works the same, just different placement of decorations.
Here is where you take your new photo and layer it onto decorative paper and add wording. Your photo should be approximately 3" x 7 1/4". After you add your background papers, your finished size will be 4" x 8".
Play around with the placement, add drop shadowing to the parts that would normally be raised, add text and there you have it! You can print two on a sheet, cut and slip into envelopes.
Let me know how yours come out! Also, can you find anything fishy in the final card up top?
PS: I was fortunate to have a tag in this design. This week's Theme Thursday's Art challenge is "tag". Check out some great tag art at: http://themethursday.wordpress.com/