Also, as I mentioned the Rock symbol was used in-show, the Poison symbol is also something that has been used officially -- it's the symbol found on Koffing. Part of why I wanted to change the Poison symbol was because it was too "skull-like."
If any symbol is going to be changed, it would be Ground, and possibly Flying (Flying to its Battrio representation). However, as I'm so far along in the project, I doubt I would change any more symbols.