Top pict here, I added the hat and arrow. The top looked a little bare to me. In the second pict, I added the paint border with some brown, blue, and hooker's green. I then used a wipe to take off the excess and make it look more distressed. Notice how I got some on the edges of the stencils and on the bottom of the bride and groom. It helps it blend together better.
Pict 3 down: I did not like the background as is. I used some transparent red oxide fluid acrylics and my finger to apply a thin layer. This is where you have to be sure your papers were thoroughly glued or it would ripple a little. I do that all the time. I thought the background now contrasted with the couple more. I used gel pens in silver and blue to outline some things. I used a red sharpie on their lips.
To me cab cards are supposed to be fun and outrageous - the opposite of the stiff and staid look they originally had. So, I added some white Sharpie poster marker dots on their face and some paint and foam stamps. I always like to include text, "I will" seemed appropriate. I tried to balance the colors and the values of light and dark. I think that the images contrast nicely with the background. Just my opinion. My composition mind at work.
Comments welcome. Have fun with your cab cards!