Unfortunately, those 'dots' all over Store icon graphics. Go to any store and click on the bottom icons that represent their different aspects - whether it's booze / items / identify / temple service, whatever. You'll notice that the icons get those same dots when you click on them (hold the click to really notice). In addition to that, the icons appear to have a buggy alpha layer, such that the 'top layer' of the icons looks corroded. I don't know how else to explain it.
It kinda looks like the artifacts (not sure if this is the right word) that always showed up on unidentified items, which was apparently fixed in the latest patch.
Comments
My guess is they didn't have original, high quality images, so they badly cropped it from the original game and slapped it here.