FLAC is not compressed .WAV.
- FLAC is a format that stores and compress digital waveforms (PCM) without loss.
- WAV is a format that store PCM data without compression.
What I'm saying is that when you uncompressed a FLAC, you're not magically getting a .WAV file. Rather, the program you're using is decoding the PCM data and writing it back into the .WAV format just because it's the most common format. Since both formats are lossless, there's no loss in this transition, but the PCM waveform could just as well be written back to other lossless formats: such as Apple AIFF and CD audio.
Due to the age and popularity of the .WAV format in both consumer and professional, it just happens - by tradition and device support - to be lowest common denominator format, but wouldn't necessarily have to be.
I hope this provides a new angle to your question.
Similarly, a lossless image is a raster graphic, or bitmap, but bitmap data is not necessarily linked to the .BMP format, which is just specific way for storing bitmap data. Just like .WAVs, the popular usage of BMP mainly derive out of their simplicity (well documented, don't support lossy content, etc), and having been around for a while.
Other common lossless formats that are also uncompressed include:
- TIFF has been around for a long time in business applications, but it is a more flexible/complex format that can be both lossy and lossless
- RAW which is found in many digital cameras can also be lossless.
In summary, there are no original format for either "audio" or "image" data, anyone could store it anyway they wish. What we have are common file formats and softwares that know how to translate between them.
To answer your question, it seems .BMP is not as much the de facto standard that .WAV got the be in the audio world. Whether the uncompressed format of choice is BMP, TIFF or RAW (or others) will depend on the type of application/business.