Looking pretty good. Here are some thoughts of each:
Republic Ground Trooper: The design is neat and the gun looks good. The legs, however, look like they would need some more colour. You could change the hip colour to white, black or dark grey, or - even better - use some white tape/sticker on the feet to make some white boots. They would look nice with white helmet and gloves.
Oh, and since blue is more the CIS colour, how would the trooper look in dark red uniform (if you have one)?
Shadow Ops clone: Cool and good-looking, but the helmet just isn't clone trooper-like. And as you apparently want be as purist as possible, I got only one suggestion: switch the helmet to a black one and use bright blue/red/green/orange tape or sticker to make a T-visor on the black visor piece. That requires some accuracy and a sharp knife, but it might actually work. Using silvery tape - perhaps even duck tape, although its structure is quite rough - might also be easier than finding/colouring red tape, for example.
Blue ARC: Well, the fig looks very good, but the gun looks somewhat odd with all the down-sticking parts. Would a sturdier design look better? Also, as you already have used blue tape, how would it look if you gave the helmet a blue horizontal bar just over the visor? You could also follow the generic design and make the middle stripe strech all the way to the chin. Careful cutting, and it should be quite easy.
Nameless droid: The design is clever and good-looking, but the head does look somewhat flat. There isn't much to do about it however, I suppose. The gun looks pretty wicked, too, although the blue sylinder might be too much. How would a grey one look instead?
As for the name, how would be
Häjy-class combat droid? Or perhaps PR1-M8 (the long arms make it look rather ape-looking) assault droid?
Seps heavy gunner: Nice weapon design, and the trooper doesn't look bad, either. The blue shirt does look a tad too bright, so I'd suggest giving the trooper dark blue shirt or at least black arms. The latter might actually look better, as it would balance the colour scheme with black trousers.
Puncher droid: Neat and simple, and a rather fun design. I would, nevertheless, suggest changing the torso to some another colour, as the yellow makes it look more a construction droid than a combatant.
Moreover, how would a minifig hand look being stuck on the back side of the droid head? Might be an useless addition, might look cool.
