I think it's a great start for an Alpha, but it's still lacking in almost all areas.
-Working on the humanoid form, your guys seem like teenagers to me, just too skinny and lacking in true muscle. I recommend getting a diagram of a human male(preferably non-nude) and setting it as your blender background, using a gun diagram to design a gun really helped.
-For humanoid movement animations, look at how you run, check out videos on youtube of peoples running animation, find every detail of a running person and animate in progressive, logical, stages. Like first do the feet, just make his feet realistic. Then make the lower back move, then the upper back, then correct the head, and finally make the arms move. Also check out Magitechs animations, they were well done and are a good learning template.
-Take notice of speed. Some animations like dying animations, lack that UMPH that looks devastating. Keyframes closer together with farther movement will give more speed. After you animate, go back and correct some keyframe placements to gain a more realistic and differentiated look. Then your units will truly hit the dust.
-For textures, try some of GIMP's nice tiled patterns, worked into pictures(use opacity to blend them). I recommend good use of the blur/smear tools to get rid of seams. Another tool I recommend is the free select, it is just great for getting specific jobs done. I also think some basic color correction helps in the overall look. GIMP also has a Bump Map Filter which combined with the free select tool and good use of the filter can make a texture look much less flat.
-The standing animations were somewhat strange.
I recommend spending a minute to make a nice pose, then copy it to the end of your animation(frame 6,8, or 10 recommended), in between edit the pose to look like he's inhaled. When you're done he'll be standing and breathing nicely.
I agree with the other guys, I think you should put a placeholder soundtrack in there. Music is a must-have for me.
I hope I didn't sound harsh or cruel anywhere.
Good luck with the mod man!