You really can't protect images on your blog (if someone wants them they can get them), but you can make things inconvenient. You can add digital watermarks to photos prior to uploading them to your site, but you need a code and there is a fee to do this. You can also alter your images yourself using Photoshop. (I started doing this to some of my photos with Photoshop, but it is time consuming.) You can also take the hyperlinking coding off the images (blogspot automatically puts an and around all images so people can click and make the pictures bigger. Shrink your pictures with image software and remove this coding so that if someone tries to copy it, when they try to make it bigger it is pixelated pretty badly.
There are right click disable codes out there. I use it for my store website so peeps can not copy my pictures or content. I tried using it for my blog, but then realized that they could not copy my button codes to grab my button so I had to delete it. I agree that also watermarking your pictures is a good idea, I do it for all of mine.