shanerjedi said:

You said yourself you thought of Princess Mononoke,

the mononoke thought was also the idea of the wood spirits (the kodama).

perhaps just something small, like removing all the ewoks chattering could make them a bit more 'mysterious'. i'm not at all suggesting that they be portrayed as small white men or anything.

also, the dinosaurs etc. if endor was more primordial, the presence of bigger badder beasts would also make the ewoks seem tougher just by their very survival.