http://www.unifycommunity.com/wiki/index.php?title=Animating_Tiled_texture

That script will step through a texture sheet. The important bit is this particular line of code

renderer.material.SetTextureOffset ("_MainTex", offset);

With that you can also write a script that animates offset over time smoothly. In fact, here's an example of one:

using UnityEngine;
using System.Collections;

public class AnimatedUVs : MonoBehaviour 
{
    public int materialIndex = 0;
    public Vector2 uvAnimationRate = new Vector2( 1.0f, 0.0f );
    public string textureName = "_MainTex";

    Vector2 uvOffset = Vector2.zero;

    void LateUpdate() 
    {
        uvOffset += ( uvAnimationRate * Time.deltaTime );
        if( renderer.enabled )
        {
            renderer.materials[ materialIndex ].SetTextureOffset( textureName, uvOffset );
        }
    }
}

For changing the image, the most efficient way is to use a tiling texture, but if you must use different source images, you can use this:

http://unity3d.com/support/documentation/ScriptReference/Material-mainTexture.html

I.e.

renderer.material.mainTexture = myTexture;

How can you control the offset with Camera.main.transform.eulerAngles.y ? I'd like to scroll the texture based on the camera rotation instead of time.

Hi, if you want animate multiple materials check this, hopes help you.