You need to undo the changes you made to the Connections code changing
src. This is valid HTML5 markup for the new picture element to support HiDPI (Retina) images. Here’s a great article on the attribute..
As you see many browsers do support it:
For those that do not, a polyfill called Picturefill is loaded by Connections to enable support.
The reason you see only the Alt text is likely you were viewing the page in a browser that does not support the new element and a bug in the theme.
It appears the theme is missing the wp_footer() template tag. This will break a great many plugins. You’ll need to contact the theme dev to have them fix that.
The single display seems to working just fine, it is using the single view of the cMap template (it has a different design which should be more inline of the theme’s page template). When you filter by the region, locality, organization and such, you’re being shown the results in the result list view of cMap.
Hope that helps!