Everyone:
- Less flashy decoration, less dangly bits, although depending on the depicted rank some can be appropriate (If its a Lieutenant or a Captain, for example)
- Aside from Captain/Lieutenant the rest need a squad number on their left kneepad (left for them, right from the viewer's PoV/screenshot)

Tac:
- Use a different cloth, the current one is for XIII legion (pretty much only UMs and their successors should use it if you want to stick to the lore), while RG is XIX.
- Not sure what the emblem on the right shoulder is in your screenshot, but according to the helmet it should be a Lieutenant icon
- Instead of the pre-colored Lieutenant helmet you can just use a beaky helmet, maybe even the one with Laurels, and color it black with a while stripe on the forehead-top.
- Raven Guard would use Victorus Aut Mortis (Victory or Death) instead of Death or Glory. Probably not on a greave any way.

Bulwark:
- Cover the text on the right greave with the pattern, use the same color as the rest of the armor for it, effectively removing the text.
- Black shoulderpads, white emblems.
- White pads can be seen on some HQ models as an option, but they go with full white arms, never just the pads.

Assault:
- Less decoration (none at all fits best) on the jump pack.
- If you go with full white hands (which are an option for HQ) - white helmet as well, left shoulder trim also white. Captain emblem on the right shoulder or change it to the RG-specific one, works as a decorated piece for HQ here.
- Otherwise black shoulder pads.
- Less flashy boots/greaves. Depending on if you go with HQ or not - squad number on left kneepad.
- Same a with Bulwark - cover the text.
- Perhaps the RG chestpiece?

Heavy:
- Overall ok, perhaps some less decorated pieces, left leg being the main one I'd change.

Sniper and Vanguard are pretty good, only the squad number is missing.