I know animated GIF's are formatta-non-grata, but it seems that a GIF with 1-bit alpha (that is, 8-bit palette with one transparent color) will load fine in the Editor. However, when I try to create such via a WWW load, I get nothing. Well I get a red ? on a white background. What gives? (I have little say over what image formats will be used, as this is a runtime loader for another common format, which allows such GIF's).
As far as I remember, WWW.texture doesn't support gif, only bmp, png and jpg. The question mark thing is the "can't load" error texture.
I'm not sure if there will be an easy way to fix it either, unless you find a gif parser (so you can pass in www.bytes to get at the gif data as another format perhaps)
Try this goods.
You can use GIF animated in Unity3D