Yes it is possible.
What you mean is that you want to specify the image that will be displayed in the snippet created when sharing on Google+. The +1 button does two things: 1) It adds +1 to the account when clicked, and 2) it does not necessarily allow the user to use your Google+ URL and comment on it.
What you are asking is the second part of this interaction and is documented at https://developers.google.com/+/plugins/snippet/
There is a tool on this page that will help you generate the HTML code that you will need to paste into your page. You can also choose one of three ways to specify fragment information.
An example of using schema.org markup:
<html itemscope itemtype="http://schema.org/Article"> <meta itemprop="name" content="My Cool Article"> <meta itemprop="description" content="This is the greatest site ever"> <meta itemprop="image" content="http://example.com/mycoolimage.png">
Bretj
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