The oldest picture I have is my deer avatar distorted by rounding errors at some height greater than MAXINT meters in Second Life. September 2005.
The deer avatar at ground level. This was one of Lucah Solvang's avatars, some of the very best early prim avatars. October 2005.
A few months later I had transitioned to Whinge Languish's stoned otter which I kept using for many years. February 2006.
The headfish was something I came up with by taking the fish out of a goldfish bowl by Starax. It got quite popular on the grid.