Graphics.DrawTexture
static function DrawTexture(screenRect: Rect, texture: Texture, mat: Material = null): void;
static void DrawTexture(Rect screenRect, Texture texture, Material mat = null);
static def DrawTexture(screenRect as Rect, texture as Texture, mat as Material = null) as void
static function DrawTexture(screenRect: Rect, texture: Texture, leftBorder: int, rightBorder: int, topBorder: int, bottomBorder: int, mat: Material = null): void;
static void DrawTexture(Rect screenRect, Texture texture, int leftBorder, int rightBorder, int topBorder, int bottomBorder, Material mat = null);
static def DrawTexture(screenRect as Rect, texture as Texture, leftBorder as int, rightBorder as int, topBorder as int, bottomBorder as int, mat as Material = null) as void
static function DrawTexture(screenRect: Rect, texture: Texture, sourceRect: Rect, leftBorder: int, rightBorder: int, topBorder: int, bottomBorder: int, mat: Material = null): void;
static void DrawTexture(Rect screenRect, Texture texture, Rect sourceRect, int leftBorder, int rightBorder, int topBorder, int bottomBorder, Material mat = null);
static def DrawTexture(screenRect as Rect, texture as Texture, sourceRect as Rect, leftBorder as int, rightBorder as int, topBorder as int, bottomBorder as int, mat as Material = null) as void
static function DrawTexture(screenRect: Rect, texture: Texture, sourceRect: Rect, leftBorder: int, rightBorder: int, topBorder: int, bottomBorder: int, color: Color, mat: Material = null): void;
static void DrawTexture(Rect screenRect, Texture texture, Rect sourceRect, int leftBorder, int rightBorder, int topBorder, int bottomBorder, Color color, Material mat = null);
static def DrawTexture(screenRect as Rect, texture as Texture, sourceRect as Rect, leftBorder as int, rightBorder as int, topBorder as int, bottomBorder as int, color as Color, mat as Material = null) as void
Parameters

screenRect Rectangle on the screen to use for the texture. In pixel coordinates with (0,0) in the upper-left corner.
texture Texture to draw.
sourceRect Region of the texture to use. In normalized coordinates with (0,0) in the bottom-left corner.
leftBorder Number of pixels from the left that are not affected by scale.
rightBorder Number of pixels from the right that are not affected by scale.
topBorder Number of pixels from the top that are not affected by scale.
bottomBorder Number of pixels from the bottom that are not affected by scale.
color Color that modulates the output. The neutral value is (0.5, 0.5, 0.5, 0.5). Set as vertex color for the shader.
mat Custom Material that can be used to draw the texture. If null is passed, a default material with the Internal-GUITexture.shader is used.
Description

Draw a texture in screen coordinates.

If you want to draw a texture from inside of OnGUI code, you should only do that from EventType.Repaint events. It's probably better to use GUI.DrawTexture for GUI code.
	// Draws a texture on the screen at 10, 10 with 100 width, 100 height.

var aTexture : Texture;

function OnGUI() { if(Event.current.type.Equals(EventType.Repaint)) Graphics.DrawTexture(Rect(10, 10, 100, 100), aTexture); }
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    public Texture aTexture;
    void OnGUI() {
        if (Event.current.type.Equals(EventType.Repaint))
            Graphics.DrawTexture(new Rect(10, 10, 100, 100), aTexture);
        
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	public aTexture as Texture

	def OnGUI() as void:
		if Event.current.type.Equals(EventType.Repaint):
			Graphics.DrawTexture(Rect(10, 10, 100, 100), aTexture)