The lemon-lavender combo sounds very good. I marinate olives rather frequently and will have to give it a try. I buy olives from the Whole Foods olive bar, creating a mix of my favorites. Typically including picholline, gaeta, nicoise, green cerignola, and dry or oil-cured.
In a saucepan I put enough olive oil to bathe the olives but not necessarily enough to cover. For about a 1# container of olives, I add:
1-2 cloves of garlic slivered
slivers of lemon zest from a half to a whole lemon (only the yellow zest, with none of the white pith)
2 sprigs of rosemary
hefty sprinkle of crushed red pepper
Let it steep for 15-30 minutes on very low heat. You don't really want any of the flavors to cook, merely to leach their flavors into the oil.
Turn off the heat and add the olives without any of their brine. Sometimes, I sliver sun-dried tomatoes and add them as well at this point. Let them sit for a couple of hours at room temperature, stirring from time to time.
I like to warm them in the oven before serving.
They will keep for weeks in their oil in the fridge. They will keep outside the fridge, too, as long as the oil covers them all.