That windows noise that Studio 12 can make when finishing a render is a useful little tool. Could it be extended to Scene Detection as well?

Are where is that "render finished" sound coming from?   I can't find the sound file under Program Files/Pinnacle. 

I would be nice to be have a customisable sound, rather than the nondescript little beep.

The sound is part of the Window Sound scheme. S12 uses the default Windows Exclamation sound. You can change it by editing your sound scheme settings. (in XP, at least).

My guess would be it uses a standard Windows GUI call to generate the beep, so changing the S12 beep without all the other exclamation events also changing might be a bit tricky.