XSI is great tool. It has great animation tools for Toon animation, and also great shaders. It’s easy to get a Toon look just in minutes. Even though it’s that easy you do need to keep in mind a few rules. Never do your image character too dark. Black is not a color for you. Even the dark blues of night would look better, believe me. The colors need to be bright, but if your characters are too colored, use simplier enviroment for them. Find colors what will make the character stand out and visible. It’s wrong to think that Toons must be colorful. Make it simple and attractive to the eyes.