In the fifth episode of the series Markus and Vaclav briefly discuss the possibility to customize the list of suggested variable names. Each time a user creates a new variable either directly or through the "Introduce variable" refactoring, he or she is offered suggestions for names. While the default implementation would offer a name based on the actual type, designers of Base Language extensions may hook into the process and offer custom-tailored suggestions. This is a good example of how MPS lets you extend languages on a very fine-grained level.
To experiment yourself, just open the JavaExtensionSamples sample project that comes bundled with MPS..