I'm testing on 0119 and found that, if setting up a P3D environment, planes
with texture applied to them, doesn't respect the z-order stablished for them.
This is being tested on a Windows XP SP2, with an nVidia GeForce GO 7700
video card.
code example:
[code]
PImage imagen;

void setup() {
size(300,300,P3D);
noStroke();
imagen = loadImage("bola1.png");
}

void draw() {
background(255);

fill(255,0,0);
pushMatrix();
translate(width/2,height/2,100);
beginShape();
texture(imagen);
textureMode(NORMALIZED);
vertex(-13,-13, 0, 0, 0);
vertex( 13,-13, 0, imagen.width, 0);
vertex( 13, 13, 0, imagen.width, imagen.height);
vertex(-13, 13, 0, 0, imagen.height);
endShape();
popMatrix();

fill(0,0,255);
pushMatrix();
translate(width/2,height/2,-200);
beginShape();
texture(imagen);
textureMode(NORMALIZED);
vertex(-13,-13, 0, 0, 0);
vertex( 13,-13, 0, imagen.width, 0);
vertex( 13, 13, 0, imagen.width, imagen.height);
vertex(-13, 13, 0, 0, imagen.height);
endShape();
popMatrix();

}
[/code]

edit]
Sketch example with its png

translate() with a z-coordinate of 100 is going to put those shapes past
the camera, where you'll get undefined behavior or the shapes will be
removed. see the reference on the coordinate system regarding this:
http://processing.org/reference/environment/index.html#Coordinates

you're also using textureMode() incorrectly:
http://processing.org/reference/textureMode_.html

There's no reference on the documentation about the z-coordinate on 100.
How does it works?

Yeah, the syntax on the "textureMode" code is incorrect but it does the
same with the textureMode(IMAGE) setted.

This code has the suggested corrections but still has the same problem: the
two shapes have the same size but the farest shows inside the closest.

PImage imagen;

void setup() {
size(300,300,P3D);
noStroke();
imagen = loadImage("bola1.png");
}

void draw() {
background(255);

fill(255,0,0);
pushMatrix();
translate(width/2,height/2,10);
beginShape();
texture(imagen);
textureMode(IMAGE);
vertex(-13,-13, 0, 0, 0);
vertex( 13,-13, 0, imagen.width, 0);
vertex( 13, 13, 0, imagen.width, imagen.height);
vertex(-13, 13, 0, 0, imagen.height);
endShape();
popMatrix();

fill(0,0,255);
pushMatrix();
translate(width/2,height/2,-90);
beginShape();
texture(imagen);
textureMode(IMAGE);
vertex(-13,-13, 0, 0, 0);
vertex( 13,-13, 0, imagen.width, 0);
vertex( 13, 13, 0, imagen.width, imagen.height);
vertex(-13, 13, 0, 0, imagen.height);
endShape();
popMatrix();

}

the reference for textureMode() is correct. the reference link i sent
explains that the coordinate system starts at z = 0, and then moves
negative from there. translating into a positive direction in z will cause
trouble. if you have further questions about syntax, please use the board,
not the bugs db.

Sorry to continue around this here, but if corrected it will still show the
farest object 'inside' the other one. I added to this example a rotation to
make this more explicit. It doesn't seem to be a coding problem.
[code]
PImage imagen;

float r = 0;

void setup() {
size(300,300,P3D);
noStroke();
imagen = loadImage("bola1.png");
}

void draw() {
r += .001;
background(255);
rotate(r);

fill(255,0,0);
pushMatrix();
translate(width/2,height/2,-10);
beginShape();
texture(imagen);
textureMode(IMAGE);
vertex(-20,-20, 0, 0, 0);
vertex( 20,-20, 0, imagen.width, 0);
vertex( 20, 20, 0, imagen.width, imagen.height);
vertex(-20, 20, 0, 0, imagen.height);
endShape();
popMatrix();

fill(0,0,255);
pushMatrix();
translate(width/2,height/2,-90);
beginShape();
texture(imagen);
textureMode(IMAGE);
vertex(-20,-20, 0, 0, 0);
vertex( 20,-20, 0, imagen.width, 0);
vertex( 20, 20, 0, imagen.width, imagen.height);
vertex(-20, 20, 0, 0, imagen.height);
endShape();
popMatrix();
}

[/code]