first person blood splatter

hey every one ,i making a Fps game in which we are kinda making the blood splatter for fps camera,,i'v made some alpha based blood textures ,and i put it as gui texture to the camera.we even achieved the switching it on and off ,so now the problem is for different aspect ratio the gui texture not maintaining the ratio.so its kinda not looking good,,so i just wanted to know how to make the gui texture resoultion frm the monitor resoultion!! thanks in advance.,.if ther is any other alterantives also i dont mind ,this blood splatter acts instead of health bar..so i need this thing to get working!!