Working off of codeMonkey's comments, I've added new patterns to my N900 and used them in new scripts. A few things to keep in mind in adding a new pattern to the N900:

Be sure to add the pattern to the LEDPatterns in mce.ini. Also, be sure to add the LED pattern to the [LEDPatternLystiRX51] section. Initially, it wasn't clear to me which section to use.

Finally, using the dbus commands that codeMonkey provided you can add your new patterns to any application you are creating or modifying.

For more details, check out my recent blog post about controlling the status LED on the N900