If a clue image is a gif it can contain another embedded file. To extract that file you need a special application that will extract the file and a password to unlock the file.
Sorry, but it is impossible to solve most of the clues without this "Hide In Picture" application. I think it should be mentioned in the main post of the thread.
Also, I noticed this software is for Windows users. Is there an alternative for Macintosh users and Linux users?