I forgot about that.
It's called the Easytex wall creator and I don't know where it's available from. We were hosting it at the official site but took it down because it's not open source and I could never ahold of the guy who made it, who's name I can't recall at the moment.
I know it's not the same thing, but if you take any of the walls for 640x480 and size them 200% of original, they'll work, though you might need to clean up some of the transparency area. (It all depends on your palette when you do the sizing.) There were also some walls made by Jörg Weber that I have. His site is the Dreamlands site. I don't know if they're your thing or not. If you want some, let me know and I could email them to you.