Looks like I'm getting to this sooner than I thought. I have indeed added a background to my Christmas fashion designs today, making them more like postcards.
You can see their full posts from yesterday- Sweet Holly Christmad Dress (left)
and Peppermint Princess (right).
For the Sweet Holly outfit, I used an existing desktop background which fit the the theme perfectly. And I made my own backdrop for Peppermint Princess by making a white and pink gradient backdrop, and added a splash of red flower shapes around the border (which from a distance look sort of like crushed peppermint candy).
Yay for Photoshop Elements in helping me to make quick backdrops for fun designs. :D