Chris Heuer says that one of the simplest ways to optimize for Universal search is to name images correctly. Not "jp_77.img," but "rockstar_tshirt" or "used_chevy_impala."
If your client sells products, make sure that they tie the image names to the product names, or even a SKU. Sounds like common sense, but Heuer says that there are plenty of companies shooting themselves in the foot with random image file names.