Can see only one picture and it looks like 'fireworks' to me.Check out the link 'B. propagation for newbies' and see if it's the same.I recently lost mine:(

Mrao, I have that begonia too and like you, I don't know the name. But I have to say, it has the most annoying habit of dropping it's lowest leaf as soon as a new leaf opens. I hate that because I only get about 3 leaves at a time. Perhaps I'm not doing something right, I don't know, but this is the only begonia that has behaved in this manner. Maybe it needs a good spanking.