Can I sue AT&T if one of their reps showed me a vulgar picture while I was making a purchase in one of the locations?

Potentially, but there are numerous problems associated with this case.  I suggest you contact a local attorney to discuss the feasibility of this case. This is not intended to be legal advice, and is general in its nature. No attorney-client relationship exists or is formed by this information. Furthermore, this does not represent the views or opinions of LexisNexis or its affiliated companies.