just a question
 

i was wondering today is it possible to make custom levels for AO and/or AE?

It is possible but it's in a very early stage as of now, look at this thread to see how:

http://www.oddworldforums.net/showthread.php?t=15680

There is everything you would need to edit AO/AE levels in that thread (doesn't mean to say that everything can be done).