Help: assign Block Texture to custom json object inside of Mcreator

I have multiple textures/runes, that i want to assign to a single object. Not as animation. 
Just a flat plane, that i want to use for different textures, like runes, sprites and so on, that i can put on floors and walls.

This is what i have. A "simple_plane" json file is added
and this rune texture should be assigned to the main/down face of
the object. But all i get is a check-board error texture.

The Model was written by hand in Notepad++, so i might have 
messed something up

Here is the JSON Model i used:

{
	"textures": {
		"all": "flashfox_decorations:blocks",
		"particle": "flashfox_decorations:blocks"
	},
	"elements": [
		{
			"from": [0, 0, 0],
			"to": [16, 0.25, 16],
			"faces": {
				"all": {"uv": [0, 0, 16, 16], "all": "flashfox_decorations:blocks", "tintindex": 0}
			}
		}
	],
}

It only works, if i assign a specific texture in the "ressources / 3d model and texture mapping" tab, but then i have to upload for each character a new 3D model.

Should i add for each sprite a seperate JSON Model for each texture? Or can this be done with a single model?
Even if there is a pre-made model, i would prefer to use my own model or else, i might be back later with a different question regarding custom JSON models.