I live in southwestern WI and toured the length of Wisconsin in September (Illinois border north to Lake Superior-had a ride home) and have a couple of ideas. You could start/finish at River Falls and explore the Mississippi River valley and Great River Road, loop into southeastern MN through the Root River valley, into northeastern Iowa, cross the river and loop through southwestern WI. Essentially a loop around the driftless area. Quiet roads, challenging hills, spectacular valleys, coulees, spring fed creeks, small towns and plenty of places to camp. Another option would be northern Minnesota, possibly some of the roads off the North Shore such as the Caribou Trail and Gunflint Trail, up to Ely area.
Randy