Currently most of the websites use text CAPTCHA image, in nopCommerce also we have textual version of Captcha image..
NuCaptcha is a first-of-its-kind CAPTCHA technology that uses video to determine if users are human...
The idea is that they’re supposed to be nonstandard enough to be indecipherable by automated spam programs yet simple enough for humans to understand and reproduce.
NuCaptcha’s technology substitutes a brief video display of characters for the usual smash or squiggle of letters. It’s definitely easier on the human eye, and its creators say it’s also much more secure.
Here are the live example/demo of NuCaptcha,,,: Click Here
It is free of cost, available in Programming API's and plugins (compatible with PHP, .NET, Java, etc.): Here
It would be great to have this latest feature (latest technique of using captcha image) in nopCommerce project in upcoming versions...