PhotoBulk for Mac
PhotoBulk is simple Mac app that has one goal: simplify batch image editing. It can batch rename images, optimize photo size, compress the image file, add watermarks (my favorite feature). The watermarks can include text, images, or dates.
Overall, it's really easy to use, and it supports live previews as you edit. If you need to resize, rename, or add watermarks quickly, take a look at it.
PhotoBulk can be bought on the Mac App Store for $9.99.