As stated, there's not really any "standard system" for sprites or tiles. The closest such thing is something like RPG Maker sprites, which are only standard because there's a community built around the game (much in the same way that there's tilesets or mods for other popular games)
That said, there's a few options. You could find a set of free graphics to use and load them into game in that format. Many times the same artist will create sprites with a "standard" layout. The downside to this approach is that your options would be pretty limited.
A potentially better solution is to use one of the RPG Maker formats. The trick is that you are NOT limited in the same way that RPG Maker is, since you can define the layout of the sprite sheet. So, you can expand on the different actions per character to be whatever you want. The RPG Maker sprites have 12 frames for each 'character', 4 directions with 3 frames of animation per direction. A lot of times, an artist would make more 'actions' for a specific character, and would simply use another 'character' slot to allow for another 12 frames of animation, or poses, or whatever.
The reason commercial games (like FF6) have unique spritesheet layouts is because each game customized the layout for the game being made. RPG maker uses a standard layout format because it's a tool to make the games, and so it needed to be able to have a standard. Unless you're making a tool to make other games, you can easily make whatever changes you want to that standard. It might require some time spent editing graphics, but when making games, it's pretty important to have skills to edit graphics files, unless you plan on only making text based game.