Annotating your images with with text or images is a very common part of photo workflow and is often the last step before publishing.
Most workflow programs like darktable and album creation applications such as jalbum will allow you to automatically add logos, titles, and copyright notices to your images.
As good as these applications are they often have some limits on how much control you have over the process.
If you want near total control over the process and don’t want to custom edit every image in your photo editing application then command line tools are your best option
