Then my friend Sara, who is a bit of a Wikipedia contributor/editor/expert, showed me how to upload the photo to the Wikimedia Commons, and then it was just a case of gluing it all together by making the edit on the Wikipedia page.
Then it was almost immediately deleted.
It turns out that apparently the Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic license (better known as CC BY-NC-SA 2.0) is somehow incompatible with Wikipedia & friends (I haven't figured out the exact ins and outs of why yet). I had to get Brandon to re-license the photo I used as just CC BY-SA 2.0 (basically ditching the non-commercial restriction). Then it magically reappeared (after some help from Sara with the response).
Crikey, this Wikipedia contributing is tricky stuff. At least when Speck's owners get back to pick her up, I can tell them their gecko is famous.