Google+ badges are getting some new duds, enhanced +1 counts and a few more size options. When Google initially released badges for users only two options existed: an icon version and standard badge version. A new darker version can be chosen for darker sites, and a smaller interactive button can be used in tight spaces. Also, all badges will feature the correct +1 follower counts from the December update.
Why put the Google+ badge on your site? Google states:
We recently looked at top sites using the badge and found that, on average, the badge accounted for an additional 38% of followers.
To create your custom Google+ badge, head to the badge configuration tool and create a custom badge. Note: Badge changes are only showing currently in Developer preview but should be available soon for all users.