I suggest that keep all images in sub-directory (i.e. images) under Application installed folder
e.g.: MyApp\Images
When you debug the project, images will not copy into Debug or Release folder, you have to copy paste them manually (Or as Matt mentioned, Select an image file from solution explorer and in Properties, Select "Copy To Output Directory" as "Copy always" or "Copy if newer". It will also keep the directory structure) and then copy whole Debug or Release folder into the device.
You can specify path of images in your application like:
// Get full application path
String full_path = System.Reflection.Assembly.GetCallingAssembly().GetName().CodeBase;
if (full_path.LastIndexOf("\\") != -1)
{
// Take away application name from full path and return current directory name
String directory_path = full_path.Substring(0, full_path.LastIndexOf("\\") + 1);
// Specify images directory
String directoryImages = directory_path + "images";
}
If you want to create an installer, then add folder and images into the installer (Or Right click on "Application Folder" under File System of CAB Project, Select "Add>Project" Output and choose "Content Files" and Press OK). When you will install application using .CAB file, it will install files and keep same directory structure of file (which are marked as "Copy always" or "Copy if newer").