Most files contained within the "dat" folder (dwc is download play as usual). The dat folder contains several nicely named files and subdirectories.
A few usual nitroSDK graphics formats (NSCBA, RGCN, nbsmd), an SDAT file (only 11 megs which is odd), some files with "SOFT" as an extension (not seen it before although I am not up on the latest games), AHX (a form of video as I recall, the ARM9 takes care of it) and a whole load of cmp files.
As cmp implies (and the magic stamp "ObjPkg" backs up) it means compressed files.
Some of the common formats are also compressed, secondly none of the cmp files compress that well (7z max settings) which is usually a sign of such things. From the looks of it a form of LZ although I am not sure if it is a custom one or a BIOS compatible one right now.
Via crystaltile2:
It seems to think LZ compression too and does it properly as well:
I have to go out though so I will leave it at that.
edit: just to save the questions. The tool I used for that pictures is nsbmd from kiwi.ds (that same guy who did loads of the sdat sound format work).
It was originally on the tahaxan forums (you have to register to download) but you can get it here:
http://www.sendspace.com/file/r9e97x
Not my upload but I stand by it.
You will also need glut32.dll:
http://www.dll-files.com/dllindex/dll-files.shtml?glut32
Note nearly every 3d file I have encountered on the DS has been compressed, I will say though if you do not know how to deal with basic compression you do not need to be doing this yet.
Did some more, work. The menu folder has a lot of LZ compressed 8bpp (GBA/DS standard) imagery. Forgive the lack of a decent palette
Also found the adx was used for some sounds in the game (hence the small SDAT file).