Well, I wanted to base this using a style that samwise (he made pretty much all wc3 original icons) uses using 1-2 colours only and high contrast o.0..(look at tauren reincarnation for that example)
It's possibly cartoonish due to the size of the head, but its more so the head looking large due to angle/perspective.
I will see if I can update the brightness of the DIS's later.
In my opinion, you should make the mammoth stand out better, as in, instead of a silhouette, it could be a bright cyan color or perhaps ghostly like a spirit. It would make perfect sense, for an ability like "Ancestral Spirit" or so, as right now it looks like a silhouette with strange highlights, completely unfitting the whole idea of a dark silhouette(although the eyes fit perfectly, the highlights on the trunk etc don't fit that well).