hey man, i really like where youre going and i have some critique!
I really like all of the lines of action, power, and energy in the poses of the thumbnails. each thumbnail evokes a specific emotion and responce which is super impressive. with B. it gives this air of raw built up power about ready to explode from him, along with great speed in a shot up battlefield.
but in your illustration, everything is different?
your rendering skills are far beyond me, so i cant crit that at all
i really like the design and i want to see it blossom!
im not really sure how to fix it, just that i think you could easily make it better!
i think study/ref of some LoL splash art for Posing, forshortening, and line of action, could be invaluable! they have a similar artstyle and mood to your render.
dont be afraid to break anatomy a little for the sake of a cooler pose, itll help keep it looser, and more powerful!