Being able to upload slightly larger files would be useful for some users.
For example, WAV files of music, or larger MP3's. I'm not thinking of MP3 sharing in terms of piracy, but for producers. I'm a DJ and producer, and for example, it would be nice to be able to quickly attach elements of a produced song onto posts on a thread in a message board. For example, if I've got a song that has a drum track, vocal track, piano track, bass track, and guitar track, I might want to upload each of those elements separately, as well as a mixdown of the whole group, so other musicians can use parts of my work for remixing the song.
That's not actually hard for me to do now, because I just FTP the different files onto my own DJ site and create a specific download page in HTML for the track, and give that link out to people whom I collaborate with. But for facilitating more general distribution by people without FTP access, the larger sized attachments would be very, very useful.
Just a thought. By the time everyone is arguing about phpBB4.0 betas, I'm sure people will look at 100meg files as "tiny".