I'm lucky enough to find myself among the several million brand new job hunters in the market. I'm still on good terms with my old employer (and wish to keep it that way of course).
I was involved with designing electronic products (PCBs, enclosures, software etc) and that is the kind of work I wish to continue in a new job. Therefore I feel like it would be very useful to be able to show potential new employers a few non-confidential photographs of some of the equipment that I have created in the past. Work that I am very proud of.
Obviously it would be grossly unethical to do so without my old company's express permission.
A set of images could be printed out on paper (that is important, so they would never be shown in a digital format) showing both the design process and the finished product working on a bench. The photos are not so detailed that one could reverse engineer any part of the product (that precaution was taken when the pictures were captured). I would keep the pictures after the interview.
EDIT (clarification)... I do not yet have copies of the images, the company does and I'd have to ask if I can borrow them. The images were intended to be used for marketing purposes (trade show stands, newsletters etc) and are entirely innocuous and sterile from an IP point of view. Some of them are even openly on the website.
I'm not planning on working for any of my old company's business rivals.
If my boss said it was OK, I'd still have to make it abundantly clear to a potential new employer that I went out of my way to get old boss's permission to show them these pictures. I'd be happy to show them written permission, although getting that is another question entirely.
Why do I need these pictures? It would be a lot easier for me to discuss the details of product design if I can have a set of visual cues for me to discuss and for the interviewers to look at and ask questions about. Also having evidence of an advanced, finished product, shown to be working is a huge reassurance to them that I know what I'm doing in this line of work. I'm not a natural verbal communicator (typical engineer) and find it hard to talk freestyle about something that is not visible to me or the audience at the time.