Unless you’re going the text adventure route, you’ll need some kind of graphics in your game. There are three basic choices – vector, sprite, and 3D. Vector graphics are made up of points, lines, and shapes. Flash, for example, uses vector based graphics to cut down on loading times, but can also handle sprites. Sprites are images made up of pixels (think NES, SNES, etc.). 3D graphics are, of course, rendered polygonal models as seen in most modern console and PC games.

Since not everyone is blessed with a copy of Photoshop, Illustrator, and Maya, we’ve compiled a few links to free image editing and 3D modeling software.

Image Editors

MS Paint
A classic. While not a particularly powerful image editing package, Paint is plenty good enough to create simple sprites. The best way to learn how to create good-looking sprites is to study existing ones, such as from Street Fighter or A Link to the Past.

GIMP – Download 
GIMP is an open source Linux image editing program, and is one of the best. A fellow named Jernej Simončič created Windows binaries for us non-Linux-using rubes.

Paint.NET – Download
A free, open source image editing tool, Paint.NET is not a bad choice for those on a tight budget (such as a budget of no dollars).

3D Modeling

Softimage|XSI Mod Tool – Download
Softimage is offering a free version of their professional modeling tool for hobbyists. The very same software Valve used to create the models for Half-Life 2 is free for you to play with – and with Valve’s plug in you can export your models for use in Source engine mods. It is also compatible with Unreal 3 and CryENGINE 2 games.

Blender – Download
I've already mentioned Blender as a tool for creating games, but at its core, Blender is a professional quality open source rendering, modeling and animation studio. It may not have the most beginner friendly interface, but if you’re serious about working in 3D, it’s a great place to start with no money (and tutorials are plentiful).

Milkshape 3D – Download
Milkshape is a very decent shareware modeler. It is less complex than the two previously mentioned programs, but that makes it a bit easier for beginners to grasp.