There are actually already ways to browse Commons images on a map, but they need significant work. For example, the tile at [1] depicts an area with easily 20 geotagged Commons images, but, inexplicably, none of them are shown until you zoom in another level. Or, zoom out to see the entire state, only to see Massachusetts shown as completely lacking any geotagged Commons images [2].
There is a ton of potential for awesome applications involving geotagged images and geographic maps. I'm glad to see the Wikimedia Foundation stepping up its investment here.