There are several locations currently online with Mars Society images.  

We are working to build a unified Image Gallery for public outreach and for use by chapters and task forces.  Please check back here soon.

Image Gallery for the Mars Desert Research Station, maintained by MDRS Mission Support team.

Image Gallery from the 2012 Mars Society Convention, maintained by James Burk.

Many other of our past images & charts are available through The Internet Archive by searching on the below url [Example Here] 
    
   http://www.marssociety.org/interactive/mars_charts.asp