A few nice Yoga fitness images I found:

Antigravity Yoga
Yoga fitness
Image by a4gpa
Strobist Info: Profoto D1 shot through a mola solo behind the subject camera right. Another Profoto D1 shot through a smaller beauty dish in front of the subject camera left.

Fitness & Health
Yoga fitness
Image by MarketeeringGroup
Feel free to use these images, but give credit to www.marketeeringgroup.com