Haha I used to worry that's why I never used to show my work now but I have a bit of a rep and people know my style so people can waster their time removing the watermark but in doing so it's a bad reflection on them and I always keep the originals - these are all hand drawn :P
Yeah most of the pieces are A4. I can't spend long on these pieces because of my busted arm (it's getting better slowly, info on my profile about the accident) so I keep them small but they still take time. I could make the prints bigger but it costs me more and the A4 ones have not all sold out so not sure it is worth it.
I have done a few larges pieces - Ludacris is A2, MJ (first one, Billie Jean era) and Ms. Dynamite are A3 and I have worked large scale in the past hope I get back in to it soon.