We haven 't seen all the provinces but how I see them in my mind then I like them all.
High Rock as a very green woodland province with hills (highlands) and a high mountain to the east towards Skyrim.
Hammerfell as a big sandy desert land much like the Saharan North Africa.
Summerset isles i'm guessing is warm tropical land as it is in line with Valenwood and Elsweyr. Pyandonea just to the south which was once part Summerset Isles is home to the Maomer who are called sea elves or tropical elves. So I guess Pyandonea is a Tamriel version of a tropical paradise like the Polynesian islands such as Hawaii and Toga etc.
Valenwood as jungle rainforest
Elsweyr as jungle rainforest on the border with Valenwood and down into the south and then turning into sandy canyons to the north.
Black Marsh as a wet swampy land with a dense mist and vines growing everywhere making it hard to navigate. Hopefully it'll have similar plants and creatures to what we saw in Morrowind which will set it away from Valenwood & Elsweyr. Hopefully it will have giants mushrooms growing everywhere being that it is a land of moisture.