I just discovered, that A5 won't load a bitmap without a given extension. A short review of the bitmap_io.c confirmed that behavior. My question is here is, why ? Every supported image format has it's file magic, so it should be no problem to try every installed bitmap loader until some had an success. I discovered this problem, when I wrote my own container format, which uses hashes instead of filenames and so I had no information of the suffix, when it comes to load the bitmap. But there's even an A5 builtin scenario, where this image loading procedure will fail. Just think of the usage of PhysFS and let the user choose a WAD archive. As you know the old Doom 1+2 WAD files only support 8 characters per file without any extension. So loading bitmaps from a WAD will fail.
I haven't looked into the audio loading code yet, but I bet there's the same problem with the extension.
So to solve the problem, the image/audio loader should
1) check the extension, and try to load the image as before
2) if no extension, try the whole list of installed loaders
I'm no sure if this forum or the mailing list is the right place for that.