Here's a quick tip for Eclipse users. When you double click on an image file in eclipse it typically opens up whatever program your OS has associated with that file type. You can configure eclipse to view images in the editor pane fairly easily, without installing any plugins.

Here's how:

1. Open Preferences from the Eclipse Menu (I think its the File menu on Windows)
2. Expand General » Editors and select File Associations
3. Click the Add button next to File Types
4. Enter *.png
5. Click the Add button next to Associated Editors
6. Select Internal Web Browser
7. Repeat for *.gif and *.jpg