Hi Madsir,
By all means, go right ahead. Editing acutal sprite bitmaps will not be part of the scope of FF4kster in the foreseeable future. Even if it were to become such, it would not happen for a very, very long time. That said, I would like to incorporate more graphics into FF4kster from the perspective of being able to read them and display them. Thus I am probably just as interested in this information as you are.
The only capacity in which FF4kster has any immediate plans for "changing graphics" would be, for example, changing what sprite a particular monster has (like, say, changing the Yellow Dragon from being the "sitting down dragon" sprite to the "coily spring oriental dragon" sprite, or to the "fat horizontal flying dragon" sprite), which is something it can technically already do I think, but instead of seeing the results how they would appear in the game, it currently just gives you some awkward text descriptions like those you see here, or maybe some numbers (i.e. Sprite 25, Palette 6 or something). Ideally I'd like it to be able to give a realistic preview of what your monster will look like as you edit it so that you don't have to keep going "change, save, load up ZSNES, fight a battle, look at the sprite, load up FF4kster, change, save, load up ZSNES, ..."
But in any case, what is not (currently) part of the plan for FF4kster is to, say, be able to draw a moustache on the dragon; or to change it into something else entirely, like a samurai or something.
We have EVEN MORE themes now, but some old ones are gone...