The first part in this is to figure out how the application knows what images are available. Since I guess that there are 0 to 10 images available, the application needs to figure out what number of images are available and their names. This can be done in several ways, but I would probably have the application call a webservice or possibly a webpage that tells the application what images are available for that property and their urls. I would then download the images that are needed, only the ones that are needed, by using the WebClient just as metal suggests. But I wouldn't use DownloadString but OpenRead or whatever it is called.
The best way to get it started is probably to pass the application the property's identification number using InitParams. After that it should be self-contained. But I really recommend having a look at the MVVM pattern. It will make it all a lot simpler. There is a lot of MVVM information online.
If you want to get started with that you can have a look at a project I have on my blog. It shows images from flickr using MVVM. It does A LOT of the things you need to do.
http://chris.59north.com/post/flickrVIEWR-A_Silverlight_2_flickr_viewer_for_blogs-pt_1.aspx
