Maybe I'm just blanking on how to do it right now, but I don't seem to be able to comment on pictures for some reason. Didn't there used to be a text box, or some reply function under the last comment on pictures?
We recently made a modification to the forum which may have prevented you from commenting or uploading pictures... this was just done today but I think we've got it fixed now. Please let me know if you come across any further problems.