Here are some ideas on how to add props and use them creatively. At our last demo we wanted to make it look like this couple was standing on a bridge or overpass in downtown Tokyo. How did we simply achieve this effect? We used a backdrop hanging pole held by one person on each side of the shot, outside of the crop. Then all you have to do is a simple square selection on the bottom portion of the picture, add a Gaussian blur, and then history brush back the people so that they're not burred also (or make an extra layer and erase back to the original).
This is one of our most classic examples of prop usage.
Sometimes the best shots come from just minimalizing the backdrop entirely, like in the picture below. If there's not enough interest, add something tasteful in the foreground.
In some cases, something just as simple as a flower can create a center of attention and draw one's eyes away from the backdrop. The backdrop usually shouldn't be the focal point, your client should. Your backgrounds will make the best photography when then fade into... well, the background.