This is a template layout for tilesets, resulting in a sheet of 8x8 tiles.

I hereby license the template and the first preview tileset under CC0.

The template was inspired by http://opengameart.org/content/complete-tileset-template by cemkalyoncu. In contrast to his template, there are no seams between tiles as laid out in the template. (Which is a fun feature, with no implication on in-game seams, just to make this clear.) Another difference is in the multiplicities of redundant variations of tiles.

The template was found by exhaustive search and is as symmetric as possible. In particular, a fully symmetric template does not exist (for the chosen multiplicities).

EDIT: Now there are two layouts. The first one is optimally symmetric with 7 tiles violating symmetry. The second one is what I first submitted, which I keep because people already used it.

EDIT 2: I finally decided on a "favourite" layout. It is the new preview.

EDIT 3: Added another preview with index numbers as in http://opengameart.org/content/wang-%E2%80%98blob%E2%80%99-tileset.

EDIT 4: The abundance of duplicate tiles is intentional: Those are the tiles that can happen to appear next to themselves. And if they do that a lot, there is bound to be a lot of displeasing repetition (depending on the actual tileset). Having multiplicities allows for breaking monotonicity of repetition. There is a flip side, though. That is why I added a variant with little duplication at http://opengameart.org/content/seamless-tileset-template-ii.