Yes ,there is a way to load external images NOT INTO THE ACTUAL APPLICATION but externally from a folder at runtime.you can refer to follow method:
public static REDocument OpenDocumentFile(string filePath);
public static REDocument OpenDocumentFile(string filePath, BaseDecoder dec);
public static REImage OpenImageFile(string filePath);
public static REImage OpenImageFile(string filePath, BaseDecoder dec);http://www.rasteredge.com/how-to/csharp-imaging/load-from-file/