Overlays cover my on-page images help

I’m wondering if I can get help with this. I would like to use StumbleUpon to advertise my blog through, however they can’t get hold of my images on my page due to errors.

This is their email response back to me:
We sent our thumb-nailer off to revisit your page, but it looks like it was defeated by the ‘overlays’ which cover your on-page images when visited.

Any advise on how I can correct this issue so that I can use stumbleupon to promote my page?

Thanks
Jolene
http://Www.wanderluststorytellers.com.au