I think you can either ask Adam to delete the photo or you can upload one to replace it in the Gallery. There is a Delete option for Album photos but I'm not finding one for Gallery photos (I know it use to be there because I've used it in the past).
Edit: If your photo was uploaded as part of a contest (world pentax day) or is in the PEG then there is no delete option. If it is just a plain gallery photo (Moved to a regular gallery from a PEG submission for example), then the Delete option is under the photo.