Oh, hell, I'll chime in. There are questions regarding the above pic that need to be answered:
i) Is this actually Zimmerman's head? It might appear roughly the shape of his head, and the jacket - I think - is similar but that doesn't help. Such a post facto photo could easily be faked.
ii) Who took the photo? Without identification, how can there be any support for verification?
iii) The blood could be plausible: there does appear to be a kind of laceration in the upper end of the right-hand bleed fan. There might be one for the left one; can't see anything through the glare. Of course, if the photo were faked, I'm sure these details could and would be added either electronically or using make-up effects. Nothing can be made of the line of blood transit, given the statement that Zimmerman was supposedly fighting on the ground; during such a contest, if it took place, blood might move around quite a bit. Personally, I'd think there would be more 'flattening' or 'spreading out' of the blood marks if Zimmerman's head were on the ground, but then again he might have risen up rapidly. Fights are very chaotic things.
iv) In the police report, Off. Smith does state that Zimmerman was bleeding from nose and the back of the head, and that he was covered with grass as if laying on his back on the ground. Off. Ayala does not make those same observations. He was second to the scene. Did he forget to mention such details or were they not observed? Would Zimmerman have been cleaned up in the interim? Does anyone have contrary observations to either position?
However, without identifying the photographer and an affidavit - and this means vetting the photographer also - the photo is utterly useless. It could easily be a fake.
The good news from the report is that there do appear to be a plethora of witnesses. Might have to wait a good long while on their statements, mind.