On my photos I have added a vignette which I like. BUT would it be better not to have a vignette? Would it be better for treasuries just to leave them normal?
The vignettes look nice on the cupcake necklaces. Your shop is so cute I don't think the vignettes matter, but you're right, having the plain background is better for treasuries.
I think your vignettes are nice - they're very subtle. In fact, I vote that you keep them - it gives them a "realness" factor - rather than your products totally just floating on white space. And I definitely think it's still treasury-friendly!
I really like the vignettes you are doing. I say keep them! They are a nice touch, but subtle enough I probably wouldn't have thought twice about it unless you said something.