If you were riveting steel to steel, it would be easy to answer- you'd use steel rivets. But the rivets aren't really the issue in your situation- you have titanium plates which are going to be galvanically noble relative to your chrome plated steel base material. And being riveted together, the two will definitely unavoidably be in electrical contact with one another.
If conditions are dry, it won't matter. But in wet locations, where the two metals are continuously bridged by an electrolyte, yes the titanium/steel galvanic couple will cause the chrome plated steel to rust more quickly than if the titanium weren't there. So the corrosion in a wet location is inevitable. If the concern is corrosion leading to failure of the rivets themselves, then I presume you'd be better off with titanium rivets. But if the concern is corrosion of the steel base metal, you're no better off either way as far as I can see.
