There's many ways to skin that cat - assuming Unix, immediate options include:
the images are stored locally, you have some mapping from filename to title, and you create new images with watermarks using ImageMagick in a bash script
or the images are hosted online, and you write a small C/Python/whatever code that gets the URLs and associated titles from the host, and then uses Imlib2 (maybe with some wrapper) to display the images with titles rendered as text composited on top
the images are stored locally, you have some mapping from filename to title, and you create new images with watermarks using ImageMagick in a bash script
or the images are hosted online, and you write a small C/Python/whatever code that gets the URLs and associated titles from the host, and then uses Imlib2 (maybe with some wrapper) to display the images with titles rendered as text composited on top