View Image Thumbnails in Right Click Menu – Windows Explorer
The ability to view image thumbnails directly in the right click menu of Windows explorer is pretty useful in a situation where you need to preview only a single image to make sure it is the right one. Opening an image viewer just for checking if it is the image you want to upload is somewhat wasting time, isn’t it? Even if you disagree, I think the ability to view an image thumbnail directly from context menu in Windows explorer is a good add-on to have.
Thumbnail in right click menu

It is FirmTools ShellExtension that will enable you to do so. There is no need to restart Windows for the feature to be applied. Once you install it, you can view the thumbnail of the image you right-click in Windows explorer within the context menu. The thumbnail size is set to “best fit” by default, but you can change it if you feel the default size isn’t large or small enough.
Microsoft Windows 95, 98, ME, NT, 2000 and Windows XP are supported.
FirmTools ShellExtension is a freeware developed by FirmTools
More about changing the image thumbnail size in Windows explorer can be read here and here.