Preview Image not showing up on Google Plus links

A few weeks ago G+ changed how they preview images. Since then when I link a post to Google Plus my blog image wont show up. The blog image is also set up as the posts featured image. According to things I read your image size should be wider than 506 which mine are (though I display at 500 – And I tried displaying at larger sizes and it didn’t help)

So when I post a link to Google Plus either i get no image option or I get to choose between my avatar or several 125×125 banner ads.

Anyone else having this issue? Any work arounds?

My site is https://beartoons.com and the most recent post I attempted was https://beartoons.com/2014/04/07/alligator-arms-defined-cartoon/