Google expanded its +1 button to Google Images. Now, when you mouse over one of the images on a Google image search result, you'll see a +1 button that lets you recommend the image to the people that follow in Google+.
"Let's say you're looking to summit Mount Kilimanjaro and want to inspire a few of your climbing buddies to join you. You search for [mount kilimanjaro summit] and switch to Images mode to find rows and rows of photos testifying that this peak can indeed be conquered."
"As with the other +1's, you'll need to create a Google+ profile before you can start +1'ing images. Your image +1's will appear in the +1 tab of your profile, where you can see all of your recommendations in one place and delete those you no longer feel strongly about," reveals Xiaorui Gan, Software Engineer.
To see +1's on the image results page you'll need to be logged into your Google Account.