Isn't that exactly what I suggested above?

The code from my Graphic class that I pasted above does exactly what you describe. Although I do have my Animation class seperate. It sounds like your approach (although handled basically the same) is quite different. Your graphic and animation class appear to be all in one. Although I am curious, how are you changing animation sequences without altering code? Animation sequence to me means, from running to walking, or dying, etc. Do you mean something else?
Creating a graphic is actually only one line of code for me: gGraphicManager->Register(new Graphic(...)); Although I do split it up into two for readability.
I'll have a few different types of graphics for my game. One will contain all tiles for individual maps environments. Like if I have a level with snow type environment, a map graphic will contain all tiles for it, including buildings, etc.
The other type are things like special effects and characters (including monsters). A single character/monster will have it's own graphic, which will contain all animations (walking, running, dying, etc.). The special effect graphics will be in categories. I'll have one for spells, for example, and another for projectiles.
Or did you mean something different? If so, could you be more specific? I honestly can't imagine having all the graphics for the game in a single graphic file, which is the only other thing that you might be talking about.