This is a pure AAC geek entry with little to no practical value for the intensive special needs classroom.
That being said here are some interesting, little known, non-standard visual/pictoral communication systems for all the other special education teacher (and speech therapist) geeks to peruse.
Elephant Memories is "a pictorial language consisting of more than a hundred and a fifty combinable graphic elements (pictograms and ideograms). It invites people from various cultural backgrounds to communicate and explore a new means of expression." I can't even begin to explain this system. You have to check it out.
Phonetic Picture Writing is another completely unexplainable system. The website states, " A phonetic picture-writing is a picture-writing, which also can be read phonetically. For its ideograms (picture symbols) are composed of special letters."
Sign Writing is a system for using pictoral images to "write" in sign language. The sign is mainly about writing in ASL, but has many links to sign writing based on other sign languages. The site is extensive, with downloads, lessons, links to other sign writing sites around the world, and information about other movement based writing languages. The associated site, Sign Puddle, has dictionaries, translation services and a sign writing e-mail service. Another useful sign writing web site is AT-Links Canada. Set aside a bit of time to explore these sites.
Instant English is an icon based system that is intended to use picture icons to teach English in a multi-sensory manner. There are free online English lessons using the system and downloads of the icons. The lessons are designed to show the images and read the text aloud.