I think your problem is that you don't finish your pieces. You need to spend more time on each one until it's totally finished. The robot could still use work and should be finished before you move on. And some detail, like bolts, seams, etc. Also think about changing the eye and mixing up the overall piece to be more interesting.
If you're short on creativity:
Give it a cowboy hat
Make a detailed jetpack on it's back
Attach it to an outlet with a power cord
Give it a mask of some kind

Suspend your pumpkin man until you finish the robot.
I would make an edit but I'm not on my home computer so I can't atm.

Move the near arm forward a bit, it looks too far back for where the leg is, but that might just be my opinion, see if anyone else thinks this before you change anything.

Great first piece! I can say that it doesn't really remind me of the metal slug games much, but I'm critical like that because they're like my favorite games. I think the main problems with your guy is that his body looks too wide and doesn't end in a narrower neck. Basically just move the collar of the shirt down and add in a neck and you'd be good.

These are absolutely amazing! The pulse weapon works extremely well, and I like the little wave it sends out as it fires. Great work here!