TubeNet

Well there's always, "Carnival of Venice". Here's a link of Oystein Baadsvik performing this on YouTube. Of course he sets the bar pretty high!

Tuba solo Carnival in Venice
http://www.youtube.com/watch?v=Y75ryZC8LB0

Check under the subject "Cornet and Piano Music" here:

http://memory.loc.gov/ammem/mussmhtml/mussmhome.html

Lots of "Air and Variation" stuff (check out the Hartmann "Variations on the Carnival of Venice"). Another place to look is in the Wright and Round collection:

https://secure.wrightandround.com/

A large number of great old-timey solos. I like the William Rimmer works, myself. The people and W&R are very helpful and they do ship internationally.

Many of the old cornet solos are also published in bass clef for baritone horn. It's easy enough to play them down an octave. I had some fun with From the Shores of the Mighty Specific with band acc. a couple of years ago.

If you remember an old solo called, Down in the Deep Cellar by F. Kroepsch, the tuba solo was actually a simplified version of the Bb treble clef solo in the piano score. The printed tuba solo is doable. I printed out the treble solo, using Sibelius, and it is amazing! Some of the octaves must be changed to make it doable. I might do it someday. Maybe even here in Vietnam.