Hi again!
I know that this is yet a quite old topic, and people are now rarely interested in it. Nevertheless I have a small plan to develop a new mapper that works for any variants of Rayman 1 (that is, the original Rayman 1, Rayman Designer and Rayman Junior).
As a first step I integrated my knowledge on map and sprites to write a program that renders both the map and events: (Yes, this is a map from Rayman Junior.)

My dream is rather ambitions as I want my mapper capable of creating custom .LEV files, modifying sprites and .ETA info. But this is basically a pastime job and it may never get finished forever. Moreover, currently I am using C# platform for the development, which is very new to me. I am not sure if I would eventually come up with any fancy program...
I will try to upload it when any useful features are added. (Currently it is only capable of rendering a map...) I hope this may interest someone, or at least contributes to this community.