The mural was painted in 2011 by Luke McCabe and artists from sessionspace, a collective of painters in Oakland who were tired of seeing the store getting tagged.
Each of the seven letters is designed to look like a California postcard and represent some part of Oakland. The first "A" is the Oakland A's logo and you can see BART and the bridge. The stuff you can't recognize (like the pig and the farm) refers to stuff that you can buy inside.
Picture from another angle.
See Oakland North for more info.