Firstly, save yourself a lot of getting fussed at: sandbox is here; drafts go in the sandbox, link to your sandbox goes in your post above. Drafts in the forums summon torches and pitchforks.
On the idea itself: anomalous cave art could be interesting, but you don't really have anything here but a standard compulsion-attraction effect. That's honestly the second least interesting way to go with this, beaten only by having it come to life and kill people.
I'd suggest doing some research into real life Petroglyphs and Cave Paintings- what were they used for? What might be their ancient creator have intended the effect upon the viewer to be- inspiring the tribe's hunters? Leading young tribe members on spiritual journeys? Letting tribe members experience the depicted scenes as a history lesson or a sort of training simulation? There are a ton of interesting directions to go with this.