Can Reinforcement learning be applied in image classification?
Yes, it can- if you have a criterion of optimality for your problem. Basically, if you can asses automatically, during the learning process, is your new result better than the result of the previous iteration.

Some examples:

https://arxiv.org/pdf/1802.02904.pdf

https://arxiv.org/pdf/1712.07465.pdf

http://www.maths.lth.se/sminchisescu/media/papers/mps-rlcvpr16.pdf

https://arxiv.org/pdf/1804.04603.pdf