in the first worm version you could edit landscapes, this is something that i truly miss because it was so cool to create a nice island for yourself and a small one for the enemy :D

there is a fan-made editor for w3d and w4 on dream17.co.uk in the forums, under the fan stuff section. it's not particularly good, but if you really, really want to make your own stuff, you can give it a shot.

where is the landscape editor on the website?

in the first worm version you could edit landscapes,
People keep repeating this but it still isn't true.

http://www.dream17.co.uk/forum/viewforum.php?f=7