Default images for article assets without photo

We are using the grid block a lot on our sites -- and using some automatic feeds that pull in content from the TownNews Content Exchange and other sources. Some of these articles do not have images associated with them. It would be great if there was an option to have a "default" image load - rather than just leaving it empty. Similar to when you post an article to Facebook without an image, your default Facebook image loads. This doesn't necessarily have to be specific to grid blocks - but any article blocks. Anyone else like this idea?