According to the various interviews with the developers, Limbo of the Lost was in development for over 10 years. The original prototype was developed for the Amiga personal computer. The developers released a few images of this early, incomplete prototype as part of a bunch of press that included a preview in Amiga Computing 88 (Jul 1995). A demo was released on one of the two cover CDs that came with Amiga CD32 Gamer issue 11 (Apr 1995).
'Dose', a Neogaf poster recognized the background of a couple of the images as being very similar to another Amiga game called Guy Spy. The poster then created this comparison gif:
Looking closely, one can see that while the images are not identical, there are clearly similarities that could not have occurred by chance. Many of the lines in the images match up exactly:
Now, it is important to note that many, if not most, game developers use art from other games and copyrighted sources during the prototyping process. In fact, there is an entertainment-industry-wide concept known as a rip-o-matic wherein creative professionals "rip" existing assets from a commercial product and hack them together to help visualize their upcoming product. Since a rip-o-matic is never sold or even shown to the public, this is a perfectly normal and legal thing to do. It is only the apparently plagiarized assets in the final Limbo of the Lost commercial product that make this Guy Spy correlation noteworthy.
A Neogaf poster went so far as to make this extremely detailed comparison image.
It is interesting to note that the characters in the Amiga screenshots bear a close resemblance to their associated concept art, while the characters in the final product bear nearly none. It could be thought that, perhaps, the developers changed their minds over the course of the 10 year dev-cycle, but this seems unlikely for the simple reason that they continued to shown the same concept art to the press -- even up to including it on the bonus DVD. Because of this, it seems more likely that no-one on the team had any strong modeling ability and, so, they were forced to use whatever existing models they could find that were close enough to their original designs. In some cases they got close, in other cases not so much.
A short gameplay video of the Limbo of the Lost Amiga demo has been posted to YouTube.