adding graphics to mods (re: blank spaces)

I've just started looking at the world editor and I have a question. Although the FAQs say that we're not able to add graphics, I noticed that many of the graphics lists (when you press edit or select in the editor) have blank spaces, where there could be an extra item or creature, but isn't. I was wondering if perhaps it IS possible to add more graphics, or if those blank spaces have another purpose (such as a place to save some kind of modification what's already available in the items/monsters/characters menu. I don't know if I'm making any sense. Does anyone (a) understand what I'm talking about (b) know how to answer this question?

 

A. No
B. No

 

hehe, funny.

Actually, I already found a few posts that dealt with this topic. If you search for 'gfx' instead of 'graphics' you'll find at least one post. If you scroll around you can find others, a few of which are productive. My initial searches turned up nothing, so hopefully this will help someone else who comes along later (and they will) with the same question.

The basic answer I've found is that it's possible to add graphics, but not easy (in fact, quite probably well over my head).