I like your shapes. You have a great balance between small, medium, and large shapes. The silhouettes are reading well.
You going to explore some action poses for the final?
Thank you for the comment, yes, after finishing the concept, I will make some action poses and start the final piece quickly, hoping to finish haha... there are any suggestions you can give me?
I would just say to incorporate some of the vibrant colors from your reference board into the final design and it will turn out good.
How to do an interesting composition and a dynamic pose for the character is something I need to figure out myself, so I can't help ya there 
I think 5 looks best, with not a lot of colorful stuff, the orange sticks out nicely and not too much, but I would maybe darken the light grays too. Also if you go for that one, maybe extend the orange of the top part to go over her other shoulder or just make sure it's visible in final, to have a bit of orange in two parts/areas. Some thoughts
Cool work! I like 4 only would hair in tone on darker . Green color as the color basis of clothing is good, it would be even brighter !
Thank you very much! I like that version! Ohh good suggestion, maybe add a little cyan and orange as a color accent too, but just a little bit in the accessories to take torogoz colors, thanks! This help me a lot!
Thank you very much!!! I realized that it is better with dark hair, I increased the brightness to highlight the color more, but it is not necessary. I will try to work more these versions and make a better design of the accessories so that the colors accent stand out. Thanks!! This help me a lot!
I think no. 2 is the most appropriate choice, but it needs a little rework. No. 3's pose is more of a defensive position compared to no. 2. If the champion is a defender, I think you should take the pose from no. 3 and try to incorporate it into no. 2 so it doesn't take up too much space in the composition.
I like your character design. Simple but distinctive. The cape looks sweet. ^^
Hey good project ! I have totally missed it until now, really really cool design.
For you thumbnails, I think the story in the #2 is the best. But I'm no sure with the composition, I personally like the #1 camera angle and #3 pose.
I'll be looking further to see what you come with 
!
Thank you ! This will help me a lot, I will try to focus more on n.2, right now it looks very messy, I hope I can improve all the aspects you mentioned to me, thanks!
Thank you very much! I hope to incorporate all the elements you mentioned, and make a better composition!
That's a really nice improvement !
To push the composition a bit further I think you could recenter her a bit. And also you should be carefull with her right arm, maybe it's just me but I had trouble to find it.
We really feel the transformation of the scarf into a stone shield !
This is going to be a nice scene!
Currently the top and bottom border seems to be pressing down on her, I would stretch it a bit vertically to give it more room.
I took some recommendations from @Oceane_Roh , @arcalie and @tj-works, to make a new sketch and define some parts!
Yeah that's really cool I love the feeling of power
