>In my opinion it would be better to pass only a reelId, a duration, a numberOfFrames.

You'd still need to specify a starting location.  The idea is to use spritesheets which might contain multiple animations.

>I would like also an optional parameter tileSize of type Object that should contain a specific tile size for the reel in the form {w: Number, h: Number}.

The animation component depends on a previously defined sprite.  The tilesize is already defined on that sprite.  What would be the advantage of specifying it here, given that it isn't optional on the sprite component?

>I think also that the version with the array of positions is useless.

You want to be able to specify arbitrary sequences of frames, so how else could you do it?