This extension allow you to display simple product's images even name,description, short description and additional information on change options of configurable products,
After installed extension, go to admin panel, clear cache if enabled after go to System->configuration->CATALOG->Catalog->Configurable Product's Image Enable as "yes" from there.
Now go to frontend and reach at configurable product detail page after try to change options on this products detail page.
Which options you will select, same simple product image replaced with main image. Also product name,decription,short description and additional info replaced with main product info.
This extension work for only configurable products.
Note : This extension will not work with rwd default theme of magento