Yes, since it's passive.
passive
ガーゴイル像に命が吹き込まれた。
命: subject
ガーゴイル像: target
(The agent is not mentioned.)
active
(誰か/何かが)ガーゴイル像に命を吹き込んだ。
誰か/何か: subject/agent
命: object
ガーゴイル像: target
EDIT:
Ah, I think I got your point. You are talking about the cases that に indicates the agent in a passive sentence, for instance, 泥棒に財布を盗まれた, right? によって is often used to indicate the agent instead of just に in these cases to avoid being confused.
e.g.
ガーゴイル像によって(何かに)命が吹き込まれた。