"Thanks for being my inspiration"
=> 제게 영감이 되어 주셔서 감사합니다. (polite, formal)
=> 내게 영감이 돼 줘서 고마워. (casual, informal)
These are slightly stiff sounding because of 영감(inspiration) which is not used that much.
If the context is known, there might be a better way to say it.