I have not tried ginger and peach, but I too always use a slice of ginger in my second ferment. I really love the flavor. Lately I've been doing ginger, elderberry and gogi berry, it's my favorite so far.
I tried making an absinthe kombucha, it failed, far too bitter, maybe I used too much wormwood.
I tried making a gruit kombucha, with sweet gale, yarrow, and wild rosemary, that is somewhat a success.
I tried making some with raspberry leaf, nettle, and spruce needle, that is actually not too bad.