If you are looking for any type of custom there are numerous others, and yes, it would be accurate to call them sub-categories.
For instance
Customs (general term for motorcycle in non stock form)
Subcategory: race
2nd subcategory
1) cafe racer, popular post WWII British motorcycles used in Europe to compete among friends and drinking buddies, styled after and using racing techniques of the day. The name is derived from "friendly" races from cafe to cafe.
2) tracker, motorcycles designed to resemble dirt or asphalt circle track racing motorcycles
The name is derived from the type of racing surface raced on I.e. dirt track oval=dirt tracker
3)replica, in the image of a specific racing machine, commonly the image of a specific sponsor or racing personality
4) bobber, popular American post WWII motorcycles, often large, surplus military American manufactured motorcycles. Unnesecary parts removed to increase speed and performance.
Name derived from the term bob, as in to cut short (such as the haircut)
Subcategory style
1) chopper, an evolution of the American bobber, emphasis of form over function
Name derived from the cutting or "chopping" of the stock vehicle to change its appearance.
2) retro, styled to take the appearance of historical motorcycles.
3) brat style, designs originated in industrial Tokyo Japan to minimalist design or older "obsolete" motorcycles that were cheap and plentiful.
Name believed to have come from the first such designer in this style.
Subcategory functionality
1) endurance, typically dual purpose motorcycles set up for extended riding distances in remote areas, including large fuel tanks and large panners for supplies/equipment.
2) street fighter/ hooligan, originally the repurposing of damaged motorcycles to road legal status at minimal cost.
3) touring. Large motorcles designed for extended range with high level of comfort and amenities.
Many many more
Trikes, stunt, freestyle, rat etc.etc.
More or less any motorcycle that departs from the factory supplied in any significant manner can be concidedered a custom of some manner
M.J.N.