Yes a vamp drones on. Everything is waiting for something else to happen. Or as used with modes........
Vamps and chord progression are two different things.
A chord progression resolves and has a V-I cadence, i,e, it has a starting and an ending.
A vamp does not resolve but drones on so the signature sound of the mode can sustain itself over the vamp.
I not sure a vamp is what you are looking for. Here are some sites that may help. http://www.riddleworks.com/modalharm3.html
This site has several screens look at all of them. It goes into detail on how to construct a vamp.
Here are some modal vamp backing tracks. http://www.youtube.com/watch?v=m37y2mltNNI
Notice they are two chords long that do not resolve but drone on so the melody can achieve the mood it is supposed to produce. You are not in competition with the tonal center of a chord progression