Two types of elemental archons can be found in the 4th edition Monster Manual. You already have a miniature of the first type with the Fire Archon from Desert of Desolation. In Dungeons of Dread, you can find the second -- the uncommon Ice Archon. I think this is one of the best uses of transparent plastic to date -- the clear plastic really invokes an icy aura to this elemental humanoid miniature.
These footsoldiers from the elemental chaos aren't shoehorned into a single role. In June, you'll be able to use this figure to represent three different Ice Archons. This soldier looks closest to the level 19 Ice Archon Rimehammer, but DMs will be able to flesh out encounters with Ice Archon controller and artillery versions
Homunculi are magically powered constructs created to maintain a watch. The exact nature of the homunculus depends on what needs watching -- some homunculi are adept at guarding areas while others prefer guarding objects. The Iron Defender is a homunculus created to guard a person.
This 3rd-level soldier protects by getting free attacks whenever the guarded creature is attacked. For the skirmish game, this is handled by the Defender ability. You may have already seen the Defender ability on previous creatures such as the Eternal Blade from the redesigned Desert of Desolation figures. If you haven't, here's how it works -- when someone attacks a different creature while adjacent to an Iron Defender, that Iron Defender can immediately attack. This encourages creatures to attack the Iron Defender before any others; a perfect example of how a soldier should work.