Yahoo has added some very useful filters to their Image Search engine. For instance, you can specify dimensions (height x width) in the search query and it will display only pictures / icons that exactly match your specified size.

http://www.labnol.org/internet/search/search-custom-size-pictures-with-yahoo-images/5224/

Searching Yahoo for image sizes or color vs black and white isn't new though. Perhaps this interface option is new. For instance, the Yahoo Image Search API already supported this for years, and in normal Yahoo search, you could also use words like "large" to trigger specific dimensions...
[Here's where this was covered in 2005... http://blogoscoped.com/archive/2005-02-25.html#n22]

As for the "recent images" feature, yeah maybe that's new, I don't know...