Maps are the same basic thing, people just rename them as they would with items, monsters or whatever.
For making new items, completely unique to your own designs I should think is going to be very difficult and time consuming because you have to draw all these images in all their possible positions. I know there are new files, mobs and images released occasionally but unless someone releases them opening onto LOMCN I guess they'll be hard to get at.
Personally If I want to adapt an existing item I'll just extract all the images for it into Paint shop and retouch them then replace them back where they origionally where. I'm guessing if you stay within the boundries of the original outline of the item there won't be a problem. I suppose the easiest thing to make a red boar green would be just to adapt the colour saturations in paint shop to the same degree with each frame of the pigs movement.
Goes to do searches, see if anyones written a guide on how to do this then integrate as a "new" mob into game
