I have 2 questions about encores. First is, do they all have to be sort of quick pieces like Kreisler or can they be longer, such as Ravel's Tzigane?
Second is, does anyone have any encorey type pieces for the viola that are original?
I think Tzigane is too long and deep for an encore.
Leave them wanting more!
I think it depends what you mean by "encore".
You could follow the path of Hilary Hahn and play the Chaconne twice as an encore.
It depends on the rest of the program.
@Paul Deck, I mean something that is originally written for the viola (ie not an arrangement).
Appalachian waltz by Mike O'Connor is available in a viola version (as well as violin and cello). Not originally for viola I think, but at least arranged by the composer.
Playing something like Tzigane as an encore might run the risk of looking presumptuous. Agree it's best to leave things on a lighter note.
Please please do not play Tzigane as an encore under any circumstances. It's completely inappropriate. Too long, too heavy, too much.
Calling your pieces from the stage may work for Vengerov, but I don't recommend it for an amateur. It would be super fakey anyway since everyone knows you don't have the kind of repertoire where you can pick tunes on the spot.