Under Utilized tree species for bonsai - as said early in the thread, what ever is locally native. I've spent way too much time with species not native to my climate, and all the problems with learning how to winter them. I won't give them up, but there is a lot to be said in favor of trees native to your own climate.
My candidates for Zone 5b
Jack Pine - Pinus bungeana - I love having a pine I merely have to put under the bench for winter. Does not need much shelter at all. Mine are still seedlings, 2nd year and 5th year seedlings, so still a long road ahead, but they are behaving nicely. Back buds up and down the young trunks. I don't think they back bud much once mature, so like with other pines, get the branches while young, and use them later when it is time to design.
American persimmon - Diospyros virginiana - another hardy tree, and they develop a nice black checked bark while still under 2 decades old. Fruit is bigger than the frost tender Princess Persimmon, D. rhombifolia, and the Princess persimmon has a smooth bark that never gets very rough. Fruit of D. virginiana is much smaller than the culinary D.kaki, so it does work for medium size bonsai. First year or two seedlings are not as winter hardy as one might hope for, but once they are 3 or 4 years old their hardiness improves. I have some seed that just sprouted, some 2 years, 4 years and 5 years, and one that was planted in the ground 12 years ago and has been bearing fruit since it was 7 years old. I'm fond of eating the fruit. Originally didn't think of them for bonsai until recently, when I saw bark developing on the 12 year old.
Local native elms, I think I have "rock elm", or maybe it is "cedar elm", and of course American elm. All are good and very hardy.
Ostrya virginiana - hop flowered horn beam - much easier than Carpinus caroliniana - tolerates more sun, heat, lower humidity and dry soils better than the "true" American hornbeam. Bark has a different look, but is quite nice, even though not as smooth as Carpinus. Very winter hardy. My seedlings are in their 3rd and 6th growing seasons. Some are approaching "pre-bonsai" and will be ready to be styled soon.
Bur Oak - is the locally native oak with a nice texture bark. Unfortunately mature specimens are hard to collect. I have a couple seedlings, and so far so good. They grow fast, back bud after a chop, and otherwise seem to be okay for bonsai culture. And are super hardy, again minimal winter protection.
There really are too many to list, the above have no issues that may thwart bonsai attempts.
Species that may have problems that may thwart bonsai attempts - so if you try the below - be aware you may be fighting a battle.
Robinia psuedoacacia - Black locust - I love the bark of mature trees, and the flowers, but I have had trouble keeping them going in pots. In a pot they are not that winter hardy, even though in the ground they seem fine.
Witch hazel, and American Filberts or American Hazel nuts. - The leaves don't seem to want to reduce.
Our native Acer - all have problems with either long leaf petioles and large leaves or problems with getting fine ramification. Sugar maple is one I truly love the autumn colors of.
Ash trees - also seem to have coarse branching.
Black willow - Salix nigra - I thought these would be easy, but have not proven to be. Lots of die back issues. They grow fast, almost too fast. Black bark and golden branches is attractive.
The reason Mr. Pall says most are literati is if left to grow naturally they abandon lower and inner branche's at an early age.
