Finding geotagged pictures is going to be tough through Twitter.
Finding tweets that are geotagged and also contain URLs pointing to images is a more manageable task.
I would recommend using the Streaming API with a bounding box around the location you're interested in, possibly filtering on a few image hosts that you specifically want to collect from. It is possible for you to accomplish this with the Search API as well. You'll have to naturally discard some results and understand the retrieval format for each respective host.