Learning Delphi by my self, I managed to create a little image viewer application for Windows, called NN-MultiImage Viewer. This application is divided in 3 parts, folder selection in the left, the preview part in the middle and the file list in the right.
The application has the ability to set a selected image from the file list as desktop background. It has, also, a preview window with thumbnails. I really enjoy this app!
The application can be downloaded from here.