HandBrake - HandBrake allows users to easily convert video files into a wide variety of different formats.
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
Ciano - A simple multimedia file converter for elementary OS.
Ralpha Image Resizer - High-speed image batch conversion tool
Any Video Converter - Any Video Converter is an All-in-One video converting tool with easy-to-use graphical interface, fast converting speed and excellent video quality. It allows you to effortlessly convert video files between every format!
Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats