I have very small hands, which I have been very conscious about. Biggest change is the thumb muscle getting bigger, as well as the palm, making my hands look wider. Fingers are not thicker, but the knuckles slightly more defined. Wrists grew thicker, although not by much. My veins have definitely popped up more, probably from fat redistribution (overall less body fat). My fists look larger in general. Also, callouses stay on the palms for longer now.
I am a little over two months on T, hope this helps.