I don't think it'd be unusual for someone to bring in piece of flash, nor do I think it'd be disrespectful.
I've brought in other ppls flash and asked to have it tattooed, but I also have always ok'd artistic liberty with colors and design.. The artist I see has done 5 pieces on me now and I trust his vision and ability and he knows I won't flip out if he changes a design/flash I choose..
I'm not a tattooer, a tattooer may chime in and tell I'm wrong, and I may be but this has been my exp.