Actually it wasn't an image proxy issue. It wasn't related to the image proxy at all. You linked an image to the gallery on your site. You need to copy the direct link to the image by right clicking and then clicking copy image address and then pasting it in the image URL box. I fixed the image in your post.
EDIT: it looks like you had already attached that image. I removed the linked one so there are no duplicate images now and they are all working.