From http://unity3d.com/support/documentation/Components/gui-Basics.html

You can use the Screen.width and Screen.height properties to get the total dimensions of the screen space available in the player.

/* Screen.width & Screen.height example */

function OnGUI () {
GUI.Box (Rect (0,0,100,50), "Top-left");
GUI.Box (Rect (Screen.width - 100,0,100,50), "Top-right");
GUI.Box (Rect (0,Screen.height - 50,100,50), "Bottom-left");
GUI.Box (Rect (Screen.width - 100,Screen.height - 50,100,50), "Bottom-right");

}

Yea this is just like in teh forums and this is NOT WHAT I AM ASKING for. I do not care about the Fucntion o nGUI crap. I'm looking for a way to change the GUI_Texture (NOT MAKE THEM) theis means I have my own picture that I need to move. I do not want to make another rectabgle. I do not care about that in this case. So I need a solution for a GUI_Texture... not GUI

If you create a GUITexture there will be a public variable in the inspector called texture. You can add your own 2D texture here. You can change the position in the transform component X and Y settings. (0, 0) is bottom-left, (1,1) is top right.

You could also follow Ben's advice, change Box for Label and add something like the code bellow in the script. This way you'll get full control of the style settings.

From Reference Manusal Scripting Guide

/* Overriding the default Control Style with one you've defined yourself */

var customLabel : GUIStyle;

function OnGUI () {
    // Make a button. We pass in the GUIStyle defined above as the style to use
    GUI.Label (Rect (10,10,150,20), "I am a Custom Label", customLabel);
}