I've encountered regular dragons of different color and skill, such as ice or fire breath, but I've also encountered Blood Dragons. Are new types appearing as i gain levels? Or does it relate to the main quest?
Not including story dragons (usually only a single fight, they are named. Can't recall them all):
- Dragon
- Ice Dragon
- Blood Dragaon
- Elder Dragon
- Ancient Dragon
- Serpentine Dragon (DragonBorn DLC)
- Revered Dragon (DawnGuard DLC)
- Legendary Dragon (DawnGuard DLC)
Thats in order of their strengths weakest->strongest. The appear based on your level. Higher level will encounter more elders. more information on dragons here