5 Methods of Navigation:

• Left and Right Clicking on Loaded Image
• File Menu Next and Prev Buttons
• Next and Prev Buttons on Screen
• Shift Left and Shift Right Keyboard Shortcuts
• File Chooser Dialogue

Other:

• Close keyboard shortcut Shift+X with file menu option
• Next image selection wraps back to the start, going left stops at first image in directory
• Uses file chooser for finding paths to items so it's universial
• File chooser has user select image, since selecting a directory is just another uneccessary step to your first image
• File Name is show in the title
• Image is scaled to Content Panel (Fit to screen style), so it scales to a smaller window
• Image can not be larger than displayable are since image is scaled to Content Panel

Note:

• Rescale of image is event based, so it will take the screen a little bit to repaint