Well, it has a Mexican "Day of the Dead" theme, and "Ixnay on the Hombre" is supposedly talking about the 60s radical/hippie bogeyman "The Man" (a ridiculous, nondescript concept that only highlights most of them were too far out of their minds to know what they were supposedly fighting against). Offspring have been quoted way back when as saying it means "Fuck the man" or something like that. If you look at the lyrics to "Pay The Man" (perhaps written and/or recorded during the Ixnay writing/recording period?), it would seem the sentiment may be more about dismissing the concept of "The Man", though ultimately humanity may control you as you try to be free - or at least there is a struggle.
As far as the 2012 Mayan Apocalypse theme goes, there are some things that are notable, even if only coincidence. The sun is central in the picture, with the words encircling it. It looks like one of those Mayan pyramids. "Ixnay on the Hombre" could also be perceived as "The End of Man (human beings)". And of course, there's the Mayan-Mexican connection, and the Mayans were a bit obsessed with death (sacrifices) and the end of the world and all that crap. Maybe the artist was conscious of that, or maybe it just turned out that way. Maybe you could say "The Man", mankind, and Mayan Calendar theories are all pretty fragile and exist as little bits of order in the chaos? LOL
I am not saying I believe in any of this stuff, but I wore my Ixnay shirt today when I saw it and noticed the parallels. Great album.