Its a good start, seems like you have an good idea of what you want it to look like, however theres a few things that could be done better:
1, he looks very flat, i would suggest maybe an dark shade or two to add more volume.
2, i wold also have a good long look at the thing your trying to immitate. Not only will you learn a few pixel techniques but make this look more authentic. For example, the originals do not use black outlines most of the way around, they use black in the dark spots again adding to the volume and structure of this. It can be a good technique to use, i would suggest using black under the legs and arms on the downward facing edges - nowhere else. The originals also have a lack of dithering. Dithering adds unneccessary texture, and considering the power-rangers have shiney lycra outfits, you certainly do not need dithering.
3, I would have a good look at some basic fundamental anatomy. The legs are too short and the head is too big and the wrong shape. Don't just draw how you think anatomy is, take 10-15 mins on google images and find some references.
4, The mockup has potential, but the background gets very monotanous. I can't remeber what it looks like in the game, but im pretty sure it was more varied. Maybe even take a different artistical direction and make a proper background (eg, forest, swamp, rocky).
Good luck, i hope to see an update sometime soon.
