This one is iffy. As best as I can determine, Batman: From the 30's to the 70's is the first instance of this cover pose, but it's unclear to me whether it was a poster insert in a comic before it was a cover. In any event, here are the cover homages, in chronological order. But first, the... original?
*******
There have been a handful of images that don't appear to have been covers, but are obviously based on it: