Then I considered an idea of adding a few pulp type Europeans after coming across the tales of Roosevelt in Brazil. Small bands with bearers etc, armed with superior weaponry and immune to magic unless a local bearer.
About 20 years (REALLY? EEEK!) ago had an idea for a race up an African river between three expeditions for a participation game, with the aim of reaching and discovering a temple. The twist being that the first group to reach it and sack it remove the wardings which release a Spawn of Cthulhu or similar - Then it becomes a race back to the boats, so the slowest on the up route would have the advantage on the return leg.
And then I found the Tekumel Project with a rather nice little race, the Hlutrgu one of the so-called Inimical Races in the Tekumel story. Oh my, do they seem to be the perfect non-human opposition for the Amazonian Indians, being a similar size, equally tribal and with the hint of the Lovecraftian which could make for an interesting range of campaign possibilities.
Little tribal bands with their own Shamans in each group, using nasty little spells, but the rub being that each spell which succeeds also has a knock on effect... Any harmful spell raises negative energy which will summon nasty creatures which will attack anything mortal. Any positive spell, such as healing or a protective charm will reduce the possibility of a summoning of something evil, or perhaps may summon a Feathered Serpent etc.
Anyway, it's just an idea which is starting to gain momentum as I look for something a little different. The other bonus is that such a project could be painted very quickly by using the right combination of base colours and washes, and so it is one of the more appealing projects I could tackle myself.
We shall see...
Check out the figures (and maybe by some here: