I had a problem that was introduced, I thought when I had updated WP, where the photos of paintings suddenly broke. Nothing I did would seem to fix it. Sometime rebuilding the thumbs would make it work, but the next day it would stop again. This seemed to be a problem no matter the theme I chose. Finally I went to the help forums and was able to find a similar issue that someone else was having, and it was suggested maybe the Jetpack plugin was causing the issue if the WP was not hosted by WP. com. Since mine is not, I thought I would turn it off and that did the trick. As useful as Jetpack is, if you are not using or configured in a way that WP . com can support your site either physically or in the cloud Jetpack can cause issues.