Correct me if I misunderstood the question, but I think this may be what you're trying to achieve?

    public Texture colorMap;//Assign this in inspector
    public Texture colorMap2;//Assign this in inspector

//The next lines will assign the above textures to the gameobject's material texture:
    if (condition)
    {
    gameObject.renderer.material.mainTexture = colorMap;
    }
    else if (!condition)
    {
    gameObject.renderer.material.mainTexture = colorMap2;

    }

Depending on the shader you may have access to other textures as well through scripting, such as normal maps, etc.