Wikipedia have an article for Plurmedio. But medio stands for environment.
You can find aŭdvidaĵaj dosieroj here and there as a translation, but a multimedia file can contain text, 3D assets, and so on, so the adjective is at best misguiding.
Komputeko also have
- crossmedia translated as plurkomunikila. Leaving alone the "cross" lexem, komunikil/a seems less problematic than the two previous one, although to my mind not enough accurate, and the PIV defintion doesn't match perfectly.
- datumportilo, constructed as "semaphore" (the thing porting some meaning)
- registraĵo which is to my mind the best option I found so far.
Maybe one may build a better word, like "ajn-daten-tipo", do "ajntipa dosiero" or "ajnspeca dosiero".
Do you know any other, possibly better, option?