Using a keyword in an image name is much better than leaving as IMG1234.jpg. When you name the image you are helping the search engines, because they can’t read an image, only the text which describes the image. The better you can describe the image the better for the search engines, meaning your images can show up in image searches. Adding a logo to each image will mean you gain more exposure when your image is shared.
In this video I walk through the benefits of naming an image, why you would do it and how.