[Wrana]

First, I would generally agree with Omnirizon about a possibility of abuse and not a great need for this (except in certain cases of old nations which don't have national summons to fill this niche maybe). Still, it's an interesting idea on its own. My ideas on this are (some you may remember from previous discussions; I would prefer to exclude things which would be obviously nation-specific such as genie...):
Fire:
I would offer Salamander or Dragon first.
Another possibility would be either Talos which I mention later or more generic Golden Statue (with Earth, Mindless, heat aura...).
Some servant of Magma King is another possibility.
Earth:
Mechanical Giant/Clockwork Swordsman - generally, they are somewhat similar, with possible difference on Enc. Stats are better than Mechanical Men, full slots, mindless, no magic. As a variation of an idea I'm toying with thought of Talos - a bronze giant with molten copper for blood Daedulos made for King of Crete. But this should be Arcocephalos only...
Ushabti (or Scared Statue if we want to escape Egyptian name). A statue of your god enchanted to move, etc. It would be based on Living Statues, but sacred and maybe a priest.
Air:
First off, here we can place an archer thug - with either some magical bow or a natural missile attack. It could be either an undead (which I wouldn't like) or a denizen of either heavenly (as in Kailasa) or faerie realms. Of course, it should get a high Precision, plus better hp than humans and higher Str (as some magic missile weapons have Str-related stats). Att/Def may be average.
Stymphalian Bird is a variation on this - requires also Earth, flies and throws its copper feathers at enemies (stats as arrows, but multiple attacks and much ammunition). High natural Prot, misc slots only.
Another possibility would be someone like Vanherse/Sidhe Champion.
Water:
In addition to already mentioned aquatic thugs, I would offer a flying jellyfish - obviously, also requiring Nature or Air, non-magical, large, relatively brittle - but with multiple poisonous attacks.
It's also possible to get character version of Claymen or Alchemical Lion (forgot how it's called - character could use name of Abraxas or something similar).
Astral:
Here it gets tricky as Astral is already powerful in late game. It's possible to get something similar to weaker Devatas with a background of a reincarnated great warrior.
Another possibility would be a Champion of Grey Order ((?), the one which contains ethereal Astral mages and knights serving them produced at special site or appearing as a random event).
Nature:
Some largish Were-creature, of course. It may also be a transformation of the caster rather than summoning spell (I would generally prefer such a way for Nature and possibly Earth instead of summons - or maybe it would be enough to make a Transformation lower and cheaper).
Satha - a giant poisonous snake with mind and possibly additional attack (or defense) with something like Mesmerize.
Maybe Faerie Champion - weaker mage than Queen, but better combatant (or maybe place him in Air)...
Death:
Already has quite enough so I wouldn't add anything here.