There are the DeLorme Gazetteers. I think most of the map data comes from the gov't, ultimately, and it's just a matter of who includes the most detail when they publish that go'vt info. DeLorme is the most detailed print source I know of. Google Earth is similarly detailed, but unless you're in one the areas with the best detail, you often can't tell what the surface is.
I've never found any maps for Michigan that are particularly adequate in terms of telling you what the surfaces are, but I haven't found a Michigan gravel road that's in my Gazetteer that you couldn't take a Wee down. I have, however, found Gazetteer-mapped roads that I personally would prefer not to take a bike down, in Ohio. If Ohio's going to improve a road they pave it, so when you do find a gravel road it's less likely to have been improved. Either way, the Gazetteers don't tell you enough about what to expect, and different states definitely have different styles when it comes to their road infrastructure. Watch out for those signs that say "GRAVEL ENDS".
