My Last Pokeball attempt for a while since I'm going to get back in Writing. This a Crystal Ball from the Ice Age preserved for millions of years and was just recently found in the present. *I don't know who's inside but it's surely is an Ice-Type Pokemon.
I love the structure of the ball, truly mirroring shape of ice. Illusion of it being frost for thousands of years is perfect, I wouldn´t be surprised if it was cold if touched.
Colour combination is also fitting, it well resebmles colouring of normal pokeball, where upper part is darker.
I also like the background which helps ball to show, for it being darker, but not too dark. Making lower part to be enlighten by ball helps a lot, I think that it both makes the ball look more stabile (when it´s visible its on something, not just flying in the air) and it also shows power of "light caught in ball".
From your pokeballs I like this most, probably because of really great ice effect. Cool work.