first off: creating a full template of this size is a daunting task and kudos bro. but making an idle sprite is the easiest part: i hope you enjoy animating. something big and realistically-proportioned like this is gonna be a BITCH to animate.
my criticism is always with the colors. bro your colors are very flat.
and what does it mean to have flat or straight colors? they don't change in hue. in other words, they're "straight ramps". dark to light within the same color.
since i just got off from work and feeling productive
(and of course my eternal quest to be best critposter in this thread) i'll actually make something.
so FIRSt i tried to just fix your colors. i was lazy though and just copied a color palette that i designed for my own sprites. it doesn't exactly work well with your sprite, and part of it is because they were designed with different style in mind, but it's hugely because of the way you are using your colors:
when i add , it's easy to see all the details that you drew (abs, collarbone, etc etc): and that's not necessarily good thing. with pixel art, you
don't want to draw the details. instead, you want to
SUGGEST THEM WITH FORM AND LIGHt.
now because of the wicked abs on this guy i'm gonna assume you want him to be ripped. but he looks grossly thin because of the way the abs are almost PAINTED ON him. the trick is
think about the three-dimensional forms and SCULPT your character.
also dude your outline is part of your sprite. it gets affected by light as well. give your outline hilights and your character will pop.
i pretty much made this from scratch using your guy as a guide:
i was gonna keep going there is always more to do but i realized i spent like an hour on this so hopefully you get the point i'm making
also i'm not going to say anything about anatomy (other than the arms seeming a bit stiff for a regular idle stance) because when you're working with game sprites i think PERFECT ANATOMY is bullshit and i'm more of the "as long as its good enough" school of thought because game sprites are all about how they animate. even then though your proportions seems pretty nicely done so i dont have to mention it anyway