DEMO: https://s29.postimg.org/mqjm99x87/Blender_Switch.gif
INFO: This tool creates a panel in the viewport that you can use to rapidly switch out objects. Simply make the objects you want to swap out into children of a control object. With the control object selected, click the “Next” or “Prev” buttons to switch to either the next or previous child object.
EXTRA INFO: The switch tool uses scaling to hide and reveal child objects. This is especially useful as it is compatible with many game engines. It is also compatible with the grease pencil, simply make grease pencil layers linked to empties and place the empties into a controller layer.
SCRIPT DOWNLOAD: https://drive.google.com/open?id=0Bwzk-fAhFYDzYXNOa1FoX2xFcUU
EDIT:
I updated the script so that it now toggles an objects visibility and render visibility. This saves on memory. I also added two buttons that will decrease/increase the resolution of textures so that the user can use low resolution images for animation and high resolution for render. Again, this is to save on memory and make production a little smoother. Just make sure your images have the words (large) or (small) in their name.
For example, Hand.closed.(large).png and Hand.closed.(small).png will be swapped out using the resolution option.