We just made live a nice little feature: easy sharing here on G2G of photos uploaded to WikiTree. (Thank you to Dorothy Cloakley and others who have suggested it.)
On the details page of any public photo you should now see a little button that says "Share on G2G" as well as a feature box below it with more detail.
A note about a likely source of confusion: this button will only appear on public photos, i.e. photos you don't need to be on the Trusted List to view. If there's a red lock icon in the upper-right corner of the photo page, you won't see the sharing button.
Here's an example of a photo details page with the button (look in the right column): http://www.wikitree.com/photo/jpg/1863_Sylvester_Bartlett_d_6-14-1863_at_Port_Hudson_LA_ae
Here's a G2G post made with it: http://www.wikitree.com/g2g/173689/shared-photo-sylvester-bartlett-about-1862-civil-war-uniform
Onward and upward,
P.S. Please help test this feature! Find a favorite photo from your collection (on a non-G2G WikiTree page, see the menu item for Images in the pull-down under My WikiTree) and try sharing it. Post here if you have trouble or suggestions for improvement.