Custom Slideshow Program

We are an event photography company that specializes in on location photography and printing. We are looking for someone to design a software program that will show the images we are taking in a full screen slideshow format, but with one catch.... The slide show program must show the LAST PHOTO TAKEN as we are taking photos. So basically the person getting their photo taken and others standing in the area can see the photos immediately after they are taken and then continue to cycle through previous photos in that folder like a standard slide show. After we stop taking photos in a session, the photo slideshow will continue to load other images from the same folder and show them in the slide show until the next photo is taken, and then THAT photo will be shown in the slideshow next and so on. It is basically a slideshow program that shows any image that is being saved into the folder next. It needs to "watch" the folder for new images coming in and then show them in the full screen slideshow immediately. The slide show of images will be running the whole time, showing all of the images shot previously that day. But as new images come in, they will need to be shown next. Setting would include selecting the image folder to "watch", slideshow speed, possible transitions, option for a text or PNG image overlay in the slideshow for our company logo or name. The only MUST HAVE feature is choosing the folder to "watch" obviously. I hope I have made myself clear. : )