Here's an update on what I've found so far: I've been working on figuring out the GDE format. I've been able to successfully extract PVR data. If it's just a packaging implementation, then it's really simple. The data is stored with a four-byte file length preceeding it. You can double check this against the file's own file length (for example, PVR files store the length of the file in the first four bytes after the "PVRT" identifier). I think an incorrect length is why some of the levels will not work (or at least a significant part of it). I've been able to extract PVR data from some of the exclusive Ecco II levels, but the first PVR file (the loading screen image) hangs because its length is incorrect (which can go into megabytes in length). I'm going to try correcting it. It should be around 250 KB. Hopefully this will allow some of the levels to be viewed. As a side note, the GDE package was an interesting choice by the developers. Because each package is completely self-contained, modifying a texture of a global element mean they would have had to recompile each package with the new data unless they had a way of injecting it in with a batch script.