Is your feature request related to a problem? Please describe.
As far as i can see, media filenames hardcoded to be:

• unique (with random suffix)
• ASCII only.

Describe the solution you'd like
Why wouldn't the app instead of adding random suffix just throw an error like there's already a file by that name, so user can come up with another unique, but quite readable filename?
Also, why wouldn't it support any other characters and not only the ASCII symbols? So you can name your attachments on any different languages.

We would really like to see any way around this as we've planned to use this great tool to send messages to our customers.