well, im seeing as it being not very creative...
like, its something dressing up as itself.
The uni is dressing up as another uni. The blumaroo is just another blumaroo.... instead of trying to be something else, which is really the point of halloween, its being something that... it... allready is.
its kind of hard for me to explain my point of view, but for example, if i Saw a specie dress up as a different villian, i would probably like it more ... well, depending on the character, and the original specie. If they used a gelert to dress up as Scarblade, i wouldnt like it, because it would be too close.... or Zafaras and Kyriis are pretty close... jetsams/flotsams, etc.
And obviously, some mixes just plain would work. A flotsam would make a horrid Scarblade. I dont think a Lenny would look very nice dressed up as Hubrid Nox.
But, if they were creative, and used a kiko as the pant devil, or an usul as Jhudora, or a shoyru as Galem Darkhand.... that'd be neato.

I asked a friend to draw for my gallery is an example of the cross-species creativity you suggest. I tend to agree.
dolphinling discovered "Hovering four-dimensional pyramid" yesterday through an SDB search. I was wondering if you guys have any ideas about what it is exactly? Or how to find an image if there is one?