The dyne:bolic distribution includes some eccellent programs for image composition and 3d modeling:
Gimp is a well mature application capable to create and edit bitmap images, offers a perfect environment for web graphics as well a powerful script engine to automatize its operations and even generate automatically stylish logos.
Inkscape is a vectorial graphics editor suitable for free hand drawing, cartoons and comics and more generally scalable graphics, realizing an ideal tool for flyers, high resolution prints and quadri-chromic prints
Blender consists of a powerful environment for 3d modeling and game development: it features a well designed interface, a ray tracing engine and scriptability of object behaviours in python: it can produce rendered scenes as well interactive applications and animations on timelines. There is allready a great comunity of artists using it, tutorial and examples are available on its website, as well a detailed manual that can be ordered online. Blender is one of the best tools in the open source and free software world for multimedia productions of many kinds, being adopted in the production of several professional movies. Using the clustering capability of dyne:bolic you can easily build render farms distributing the load on several computers on the same network, see the Spot's tutorial available online on http://.
GQview is an easy to use image browser which you can also use to build slideshows to interactively show your image galleries.
ImageMagick is a set of commandline tools, starting from the convert terminal command (see man convert) you can easily script batch operations over multiple files, applying format conversion and filters on large quantities of images.