This is just a simple image viewer that I made in Visual Basic. I began to hate having to open either photoshop or some other imaging program just to view my images and I didn't want to go scavenging around the web for programs that say they can do it all. Because of this, I made the simplest one possible. You click inside the window to open an image, even if an image is already loaded. Images will scale to fit the window, but will keep their width to height ratio, so images won't look all distorted. Use it however you want.
To make it the default image viewer, right-click on a picture -> Open With... -> Select your program -> Check the box that says "Always use this as default" -> Open!