@flatline: Two possible options (1) you are not using the latest (or the same, if there are more than one) DDS plugin and GIMP. I'm using DDS Image (file-dds-save/file-dds-load) by Shawn Kirst, 2008. As for GIMP, I'm using 2.8.2. However, more likely is (2) I think, where you might have ticked the "don't ask me again" box on the DDS load dialog, which presumably uses the last settings you had selected for all time. I'm afraid I don't know how to reset this option, but there must be a 'reset plugin settings' button somewhere.
Alternatively, you could try out this plugin (
http://code.google.com/p/gimp-dds/), which seems to have a few more features and be more up to date.
@Starnick: Cool to hear that you play Grimrock. Ahhh, I see now why it's a conversion API and not a full scene exporter (as it's readonly). I guess when you started working with an Import library, you never imagined that you would need to edit the scene graph (a reasonable assumption). It's cool to see Assimp moving in the direction of exporting too however, as engineers have already figured out how to map those file formats to the Assimp Scene graph, it would be really powerful to be able to do the opposite. Not a quick job though I imagine. I'm gearing up for a move to Canada over the next couple of months, but when we get there I might have a decent amount of spare time I can offer if there's anything I can help with (the GMT should've calmed down a bit by then too!).
@flatline: Haha, I like where you're going with the starved prisoner. The face looks a bit creepy (would fit well in a horror based mod). Hehe. Good work.
@LordYig: Yup - the toolkit will provide full Rigged FBX -> Grimrock conversion, including animations and bone weights (I've not figured out where these are stored in the FBX file yet - but they must be I'm sure

). I was thinking down the line you could setup the GMT to watch a folder for FBX files and auto-convert them for you when you export a new one. That's a long-term feature though (lets get it working first). Unfortunately, 3D model formats are fiddly little guys, and I've not yet figured out the best way to get rigged models imported using Assimp yet. I expect support will be better when I upgrade it to Assimp 3.0 (thanks to @Starnick) and there will be loads I can do too to improve support for the edge cases. The wisp.x file did just import fine though - I did nothing special with the fact it's a biped, just read the bones out of the model and added them to the Grimrock version of the model (all just imported through Assimp). So some settings must work!
@Moutrave: Grimrock model meshes are broken down into 'segments' and you can only have one material per segment (one diffuse texture). However, you can use the same material across all of the segments in your model if you so wish. For instance, you could have 6 cubes as separate meshes in your model and each could use the same material definition (and hence texture). Moreover, your texture might only be a single face of the cube, and you could map the UV coordinates for each face to the entire texture so that the full face texture appears 6 times on each cube (and 36 times across the whole model).
It's not possible (at least, with the GMT and I don't think the models support this) to overlap 2 textures on top of each other on a single face. Hope this answers your query.