The features let users add comments to friends' check-ins, and attach pictures to tips, check-ins, and venues. The latest additions are incorporated into users' history pages and blended into all users' activities.
Only Foursquare friends can view the comments, but photographs on venues can be seen by everyone.
The site will prompt users to add photos when they check-in, just as they currently are prompted to add a "shout" with each check-in, the company said. Users can add comments during the check-in process.
Foursquare worked with several partners on the photo feature.
"Photos from Instagram pushed to Foursquare will now be check-ins with photos (rather than just check-ins)," Foursquare said in its blog. "Sightings on Foodspotting will be check-ins with your food photos. And picplz is the first service to allow check-in photos on both iPhone and Android."
The geolocation service expects these new capabilities to be available for Android users later this week, the company said.
"There are a couple features we weren’t able to fit in for this release but we’re working to launch soon. These include sharing photos (to Facebook and Flickr), an easier way to keep track of all the comments you’re getting, and a more useful place to store all your old photos (right now, it’s all on that history page)," the company's blog said.