The Song Rhythm Tracks service currently supports about 60 different distinct rhythm categories, which includes about 250 distinct rhythm types.  Most of these are available with differing instrumentations such as ‘rim’ shots or, say, wooden blocks, and many are available at multiple tempos.   Each variation may be considered a unique rhythm option.   In all over 3,700 different rhythm options are available that can be applied to a song form.   The app makes selection easy by providing filtering on a musical meter (say 4/4 or 3/4 time), and feel (even or straight, 8th or 16th notes) and provides a two-tier categorization for selection.

Here is a tiny sample of the styles represented:

For a full list of all rhythm categories and rhythm types available, see the page catalog-rhythmic-styles.